I absolutely love this place. We have Jeep's and Dodge chargers. They are masters of that type there. American Muscle baby. Stay away from trash dealers who literally wanted to charge me twice as much. I didn't even call these guys the last time, I just rolled in and they always go above and beyond. They are geniuses and honest and reliable and I will never take my car anywhere else. Don't be an idiot. If you got a high performance car or an American made bad ass, go here. You won't regret it. read more

Grc Performance - Dodge Charger SCAT PACK tuned up courtesy of GRC baby!!!! - Auto Parts & Supplies Near Me - Mission Viejo, California

Extremely rude and unprofessional. Came in earlier in the week to set up a time to bring the car, was told to bring it first thing on Friday. They didn't get my name, number, car info, or anything. I come in on Friday morning and there are 2 cars so I have to leave the car and come back 2-3 hours later to just get them to look at it. After a quick glance and reading the CEL code they told me that the crankcase ventilation is disconnected which I already told them earlier. They looked and said it would be $125/hour to diagnose the issue with no idea on how long it would take. I agreed and asked if they can do a discount at the end. He then told me off and said that the vibe wasn't right. He followed with saying "thanks but no thanks"! I understand if they don't want to work on a car for any reason (not their specialty, don't know the problem, don't like the car, whatever...) but that's no reason to disrespect someone who's trusting them with their car and is paying them a lot of money. Believe it or not, paying someone $125/hour indefinitely is not a bargain and getting paid to work on my car is not a favor. I recommend skipping dealing with them altogether and just going somewhere else. The OC mechanic down the street is nice, they talk to you like a human being and they actually care. read more

2nd WORST performance shop I've ever worked with in over 50 years of doing Car Guy stuff. Doesn't stand behind his work. Put me off for over 3 months to bring back my car after it had problems with the work he did. One bad excuse after another. Avoid at all costs! read more

Very attentive to what the issue was and willing to work with me on scheduling. Got me in and out quick

I just had to post this additional comment about my X-pipe installed by these folks. I have had so many really positive comments about the sound of my car, but recently a guy in an absolutely beautiful Dodge Viper stopped next to me on Wilshire Blvd in W. LA. He signaled for me to roll down my passenger side window and commented on how great my car sounded. And that coming from a Viper owner. I'd say that was something. read more

I took a 2019 Toyota Tacoma Off-Road to have a 2" leveling spacer put on in the front and a 1" block in the back. After doing some research on the task on Tacoma World Forum, I had a good idea how much labor was involved. Umberto quoted me a very fair price over the phone. It was considerably less than Allen Tire Co. which is a few doors down. The company I work for is down the street from Allen Tire and we do a lot of business with them with our trucks, and they still were very unreasonable. Smh. Thanks Umberto for doing a great job. The staff is really nice as well. I'll be a future customer. Thanks GRC! Jeff read more

Grc Performance - Auto Parts & Supplies Near Me - Mission Viejo, California

Umberto has been my friend and mechanic for over 10 years now. He's one of two people I trust to work on my '32 roadster, him and the guy who built it. He's, of course worked on all my mustangs over the years but also my Ferrari Modena and last night he installed a Fabspeed xpipe on my Porsche 997. I've always found him to be competitively priced but for me, knowing it's done right and that my wife and I will be safe after he's had our cars is more important than finding the cheapest guy on the block. If you have any kind of performance car you need Umberto's number in your phone. He's never let me down. read more

Umberto built my 66 Mustang about 5 years ago. We swapped out the stock 200 and added at 302, T5Z, 9" rear, and upgraded suspension and converted to 5 lugs. I don't let ANYONE else touch her. Unfortunately last year I had a rear seal leak and I was too far away to tow. I had to have someone else repair and it's been a nightmare for the past year. This week I brought her back because the leaking started again amd vibrations were getting worse. Umberto got it back to the way it should have been.....and it took less than half a day! I also take my daily drivers to him..... Best prices and repairs and service I know will be done right! read more

Grc Performance - Built by Umberto at GRC. Highly recommend him for builds, and regular service for your daily drivers. - Auto Parts & Supplies Near Me - Mission Viejo, California

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When I came to GRC my '68 mustang was so rusted it wasn't safe to drive. I had 3 shops give me a recommendation and Umberto was by far the most honest and accurate of them. From major fabrication to building an engine from scratch, everything was done by a man that treats cars like artwork. I didn't tell him, but I had a highly recommended shop inspect the car when it was finished and they said they couldn't match the craftsmanship! Not sure what more you could ask for? read more

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I have a 2005 GTO with a LS2 engine. My car was running sluggish and was out of alinement, also it needed new tires. I brought my car in on Wednesday told the owner what was going on and he got straight to work. Every time he ran into a problem he called me to inform me on what was happening. I told him a budget and he stayed well below my budget and had the car up and running on Friday. Very please with the customer service. When I picked up my car I could tell from the idle it was already running better. On my way home I was able to open the car up and the engine was more responsive than ever. Thank you so much GRC Performance. This will be the only place I take my car from now on!!! read more

Took my mustang to 2 other shops for them to finish up the engine build and one shop took 5 months and the other shop took 6 months, barely did any work and charged me $1,200 (5150Racing). Took the half finished engine to GRC and they got it finished up, and put in the car and running within a week, let alone the transmission rebuild and brand new clutch. Thanks guys read more

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GRC Performance is the place if you want to Supercharge your car. I have a 2016 SS Camaro and I wanted to install a supercharger but I wasn't sure of which one to buy. With Sylvia's & Umberto's expertise they helped me decide which way to go. I left my girlfriend (the SS) at their shop & went home to my wife. Sylvia called me a few days later & said my car was ready. I'm blown away by the increase in horsepower. At half acceleration the SS is scary fast, at full power it's pee your pants fast. I went from a muscle car to a super car in a couple of days. In all my years of dealing with speed shops GRC is by far the best. Umberto really knows about high performance cars. He is absolutely the best! The install looks like a factory install. As Sylvia promised my car was done on time & at the price quoted. I trust both of them so much that all my mechanical work on my cars will only be done at GRC Performance. Thank you Umberto & Sylvia! read more

Grc Performance - SS Camaro Supercharged - Auto Parts & Supplies Near Me - Mission Viejo, California

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I Brought my 2018 F150 here for the first time last week and met Umberto and Neil . They did such a clean job installing my snow performance kit. All the wiring was done nicely and professional. I went to the professionals to have it done the right way and I feel like they went above and beyond to make sure it was. I definitely recommend this shop. I will be back for more work soon I'm sure. Thank you all for taking care of my truck. Brandon & Family. read more

Brought my 2006 mustang in for a kenne bell install. Put 70,000 miles on that car without a hiccup until a drunk driver hit me. Ins co paid me and now I have a 2014 5.0 that Umberto will be upgrading and servicing. I've been coming to GRC for 10+ years and they have been honest and trustworthy. I will continue to bring my car here. read more

Grc Performance - Kenne Bell on my 06 mustang - Auto Parts & Supplies Near Me - Mission Viejo, California

Another great experience from the crew at GRC, had a performance tune and Diff service done on my 07 mustang GT, very professional, competitive prices, always done right the first time will definitely return for other Services read more

While my experience occurred many, many years ago, it still bothers me to this day. I brought my '99 Cobra in for an engine rebuild when I was just 20 years old back in 2003 or so. It was my first muscle car and I was really excited to do a built motor. I got a quote to have a forged engine build done and let these guys go to town. I had saved up money for two summers to get the work done. The first major issue was the time they took. They agreed to six weeks and the project took months. This was my only car at the time and it was a big hardship to have it gone beyond what was planned. Many phone calls and in person visits later, I got the car back. Upon starting the car up, I noticed a very loud ticking noise. I made a comment to Umberto about this and he told me that it was "the lifters just needing to fill up". Not convinced, I talked with him about it for a while and he assured me that the car was fine. I left feeling a bit worried about it but I trusted his word and hoped for the best. After 1 week of driving, the noise was worse and I called Umberto to discuss the issue and he didn't call back. After many calls, I finally drove the car down to the shop to have them look at it. I sat there for 4 hours waiting for them to look at it and they told me that the car was fine. Umberto again assured me that the noise was temporary and that it would go away after driving the car for a while and slowly breaking it in. I again left unconvinced, but agreed to continue the gentle break in period. After another week, the noise was still there and I called to make another appointment, fearing that the car was near to some sort of catastrophic failure. Umberto told me that he couldn't see the car for two weeks and I booked an appointment. One week later the engine blew up. Upon calling GRC to let them know of the failure. They said they would look at it but that I would have to pay any labor charges to have them do so. After pointing out that I had continually been calling them with concerns about the car, they refused to do anything but a paid tear down. I refused. After a number of discussions with Umberto trying to convince them to do me right and fix what was clearly their mistake, I finally decided to take them to small claims court. This was really my only option. In court, Umberto proceeded to tell the judge that I had, "installed a nitrous system on the car and spun a bearing". Where he came up with this was beyond me! In fact, how he would know that a bearing was spun was pretty incredible given that he had never even inspected the car! No nitrous ever touched the engine either. The actual problem was discovered to be two fold: 1) too much side clearance between the rods and 2) the cam journals had been tightened down so much that the cam ground into the journals and clogged up the oil holes, causing the cam to seize and timing chain to snap. Unfortunately, the judge chose to side with the "mechanic" over the word of a young kid and I was left with no money and no car. Those are the facts, as they say. There are many great shops is Socal and I suggest that anyone with any sense at all go elsewhere. And to Umberto...dumb, dumb, lying Umberto... There is a special place in hell waiting for pieces of you-know-what like yourself. Good luck to you! read more

Apparently you can get sued by giving a bad review, from personal experience, about a business; this is what's potentially going to happen with me. I originally gave GRC a 5 Star Review with much praise, but then I updated the review a year later with a 2 Star Review. I received a call from a paralegal, Charlie at R&K Law Group who is representing GRC Performance, he stated that if I do not delete my review I will get sued and they will take me to court. So, I took it down. read more

It's been a very long time since iv been ripped off, but I have NEVER been ripped off as bad as these guys did me. I bought a car and it was having some engine problems. They told me it was "X" problem so I had them fix it. A week later the car started acting up again, took it back and they told me it was now "X2" problem so I had them fix it. This happened 2 more times with "X3" and "X4" problems. After over $2000 in repairs, I decided to go to one of those chain places, that ironically, I wanted to avoid due to the high rip off rate. They checked the car and said it was the original "X" problem that was NEVER done by GRC!!!! They even gave me a deal on the job and BOOM! The car runs perfect. They told me the other problems were caused by the original problem and should not have been "fixed". Do yourself a favor and go ANYWHERE ELSE but here. I know its enticing to go to a "specialty" shop but do your research and DONT GO HERE!!!! for American muscle there is a shop in Aliso Viejo that is honest and will NOT rip you off, its called EXTREME mustangs.... read more

Why would one have to set an appointment for a dyno appointment and then be asked to remind them days prior to going? Okay no problem I'll stay on top of that, but then to show up right at their opening hours which is 10am and the owner and employees stroll in at 1030 to begin moving cars... Once they finally pull my car in (mind you when I set up the appointment I had advised the tuner the modifications on my car and what we needed) they decide to tell me that they need my car for 10 days to get the tune right and that it is more to tune than they had expected. Don't show up to your own business late and then tell me you have too much other shit to do that was scheduled when I have had my appointment for nearly a week and had to remind you about my own appointment. Never recommended this place to anyone and surely will not considering how rude and inconsiderate they were. read more

I've taken my car here a few times now to get work done. Each time Umberto has worked quickly and has done an amazing job on my mustang. The front Desk here is also very helpful and informative answering all my questions. I will definitely be returning here for future mods. Thank you!!! read more

This is the shop Tuttle Click Ford sent me to when my Shelby was too much for their mechanic to deal with. It is a 'little' modified - 2006 GT500. Umberto has fixed ALL my issues - fixed my headers, cold air & tuned it correctly. His prices are fair & his work is outstanding. He even washed my engine. If you have a Mustang - this is THE place. read more

Great and honest shop. Humberto is knowledgeable efficient and honest with the work that he does. The quality of work is excellent and I would recommend GRC for all makes and repairs. read more

I refused to take my ZL1 to the dealership when I ordered it brand new. Dealers will typically rip you off and I don't trust their sometimes "careless" nature. I was fortunate to find GRC early on in my car build project. Umberto has worked on my ZL1 for years and always done great work. He and his wife are super personable and go the extra mile to ensure you are taken care of. I'd highly recommend them for any service big or small! read more

The deal is this: finding the right mechanic for the right job is tough. I have a 1977 FJ40 with an 84 GM engine and a fuel-injection mod. My last mechanic fiddled for years with it. Years. As in, the thing was at their shop for years. When they finally got it running, they managed to do everything so wrong and half-assed that the FJ made it a month before it stopped (wiring, fuel, etc). I finally did some research for a mechanic who had experience doing custom work. This takes more creativity in a mechanic than the regular dealer-style guys. Here is my review then, of this shop: Firstly, there is a two person team at the top: Umberto and his wife. The wife is who you want to talk to for scheduling and billing, etc. She is the social side of the business, and she's super nice. Umberto is more like a genius who doesn't talk much, but when he starts on your car, he will work late into the night (not kidding) until he can't do any more, and then will keep on that until everything is as cleanly set us as it can be. He will call and discuss the situation as needed, and he is all business (a pro). It is obvious he knows his business just from the questions he asks. He isn't cheap (no good mechanic is). But dang, he knows his stuff. He is now my mechanic for anything I cannot do myself, especially on custom applications. He just gets it. read more

I will start off by saying I almost didn't go here for my dyno tuning because these reviews were so bad. I started asking around to some people at cars and coffee and they has good things to say about grc performance so since my car had so many computer problems I couldn't fix myself I thought I would at least give them a chance, I'm really glad I did my experience was great the owner and mechanic did everything to help me get my car back in action and after dyno tuning more power than ever. I would highly recommend for all hp junkies especially all you 5.0 guys 448 hp I'm satisfied for a little bit but I'm sure I'll be back to get 500 thanks. read more

Grc Performance - Grc dyno run - Auto Parts & Supplies Near Me - Mission Viejo, California

I was a kid when I took my mustang to this place. Umberto was there. This was in the late 90s and I'm still bothered by it. He said he could fix the car but rearranged my wiring so it looked better........$500. I was young and didn't know much but wanted my car back so I paid. How stupid I was. He's a crook. I can't believe they're still around. read more

I don't usually do reviews but in the case of GRC Performance I felt I had to make an exception. I have known Umberto and Sylvia for 19+ years and these are honest down to earth people that I trust. I own a 2001 Mustang Roush GT that have been upgraded in 2008 with a 2003 SVT Cobra drivetrain. If you know anything about these Roush it is the pain in the ass low stance with the side skirts that demands care and skill to rack, or risk tearing up the ground effects. I trust no one with my baby. GRC Performance is the exception and almost all of the work done to this car for 19+ years have been done by Umberto. PERIOD. They posses the patience and skill to correctly diagnose and fix any issues that I've experienced with my Roush. The passion for what I want in my car shines through with collaboration of my expectations with the shop to deliver exceptional solutions. My Roush continues to be my daily driver, thanks to GRC Performance. read more

I took my Custom Ford to GRC to have some minor modification work done as this is what they advertise as being their specialty. I also needed the brakes repaired. $1000.00 later the car ran worse than it did when I took it in. When I called them about the problems they were rude and reluctant to let me return the car to try to find the problem. After the car died and refused to start, I had to call a tow truck. When I called GRC to tell them it was coming in, they said not to have it sent there. They refused to do any further work on the car and told me to take it elsewhere. I've never been so rudely treated nor wasted so much money!!! The next place I took it to fixed the problem promptly and much more reasonably. read more

Let me first say that I sold my 1998 Cobra a long time ago, BUT my negative experience with it at GRC has never been forgotten. AT the time, I was relatively new to the after market performance experience, however, I saved up money to get a supercharger installed. I was only 23 years old at the time and I went with the Procharger self contained oil system they recommended with 10lbs of boost and 3 core intercooler system. First off, the installation took way longer than expected 3-4 weeks with every excuse from the book thrown my way. Those excuses were NOT from Umberto, he was actually a cool guy and he seemed like an honest guy. The excuses were always from his I believe older brother (I forgot his name, I think it's Phil) but he handles mainly the "business" side of the shop. Secondly, the fuel pump installed with my kit was bad from the get go, BUT instead of ordering a NEW one, they simply grabbed a USED one that they had lying around the shop out of another mustang! And they even admitted that!!! At that point, I just wanted it to work and be out of there. The next issue is the MAIN reason why I'm writing this review. I was on the highway one day about 2 weeks after getting my car back. Got on it in 3rd gear and heard a loud bang. At that time, I did not know what had happened and there was a constant rattle from the car. I decided to take it back to GRC because they are the "mustang specialists" and have them diagnose it. They said that it was a "blown head gasket". They even brought me back into the shop and the guy had a gauge (I think he said to test compression) on it showing me different readings and the reason why they thought it was a blown gasket. Obviously I was VERY naive back then and didn't know a thing about motors, so I trusted them. Since my Cobra had barely 37,000 miles on it, THEY recommended to see if I could get it warranted by the dealer....BUT they would have to take the supercharger system off before I took it in so as to not void the warranty since according to them at the time there cold be "major" engine damage. So obviously I agreed. Turns out, it was NOT a blown head gasket at all, but a HEAT SHIELD from the exhaust underneath the car that was rattling. There were no check engine lights and the FORD mechanic diagnosed it during the initial ride along. What pisses me OFF to this day is that the owner (I think his name is Phil) actually CHARGED me over $600 for the labor to take off the supercharger system and then put it back on!!!! He said he was "giving me a deal". It was their fault that they misdiagnosed such a simple issue in the first place! For "mustang specialists", how can you tell me it was a blown head gasket, scare the hell out of me, sell me on it using gauges knowing I knew nothing about engines, when it was NOTHING close to that?!!! I felt like they took advantage of my naivety and me being a novice. Anyway, I would NOT recommend GRC to anybody. Good and honest businesses DON'T take advantage of people. Nor should they EVER use a USED part in a supercharger system that I paid over $4000 for just to get me out the door. Side note....I ended up taking my Cobra to Chicane Sport Tuning, because my "used" fuel pump that GRC installed FAILED about 2 months later. Joe Chicane diagnosed and fixed my fuel pump immediately. It was very unfortunate what happen to Joe, but he would be who I would have still recommended TO THIS DAY for any Mustang performance lover! I just had to get this review off my chest after all these years and thinking back to how I was MISTREATED and TAKEN ADVANTAGE of by GRC. So find someone else to go to. read more

I am baffled by some of the poor reviews here, and they are NOT the GRC and Umberto that I know. I have been a customer for over 10 years, they have taken care of three different Mustangs, and now the take care of all the non-warranty work on my daily drivers -- brakes, transmission service, oil change, cooling system, etc. Their work is always top notch, the prices are fair, and Umberto always takes the time to answer questions, and spend a few minutes shooting the breeze about his BOSS 302. My conclusion: The negative reviews are all lies, posted by the competition. GRC has my trust -- 100%. read more

I took my car for a routine check and was given an honest answer and a great deal on routine maintenance. Thanks for the work I will be going to GRC from now on. read more

I first brought my Mustang to Umberto 13 years ago and have been going back ever since. He always does an outstanding job. He is extremely knowledgeable and willing to provide more detailed answers and explanations than any mechanic I have ever dealt with. I trust him so much, I bring my BMW M5 & X5 to him for all routine maintenance. And when it is something he thinks a specialist should look at, he is honest enough to let me know and to give me the knowledge I need to deal with someone else. I would and have recommended many friends and family to him! read more

GRC Performance is great. Umberto and Silvia make a great team. They really know a lot about Mustangs old and new. I was very happy with all the work I had done for my 2012 Mustang at GRC. I highly recommend this shop. I will get all future work done here. Also the prices are the best in town. read more

GRC put in my Ford Racing lowering springs. They took extreme care with the car and it looks amazing, drives super smooth, and handles unbelievably. Thanks Umberto. Great service at very very reasonable prices. read more

Grc Performance - Beautiful stance. Quality work. - Auto Parts & Supplies Near Me - Mission Viejo, California

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Worst experience ever. Rip off artist who lies straight to your face and takes more money than required to do a job.

Took my car in for maintenance and got awesome service I highly recommend getting your work done here

They did a good job on my husbands car. He was happy as for my, I just didn't care for the way the owner talked to me like I didn't know what I was talking about when I took the car in. but other than that we are going to bring our other cars here, i just won't be the one dropping them off read more

I just drove home in my fixed car (that had a faulty sensor) and was compelled to write a review...GRC Performance deserves five stars for multiple reasons. They are ethical, ethical ethical! I do not know anything about cars, but the wonderful staff at GRC has never taken advantage of that. Silvia is also an absolute joy to work with, and her husband, the mechanic and owner, does a stellar job! They have never done any work to my car that didn't need to be done. I also compared GRC quotes with another local mechanic and it was apparent to me that GRC's work and parts were quoted at half of the cost in comparison to another local mechanic! Six months ago I made the switch to GRC Performance and have not looked back. I highly recommend them! read more

I've gone to GRC for multiple installments into my scion Fr-s and they have great pricing with a quick installation time. There is no other place in Orange County with the professional experience and convenient prices like GRC has. Great business, great people highly recommend. read more

GRC Performance is not reliable place. Sylvia the owner told me that they would put a LED light and they put regular lights on and she said she would give me a call back and she hasnt. I would not recommend GRC performance whatsoever!! read more