When my truck had issues with the exhaust system, we had it towed into Holly. I was told that it was Gas in my diesel tank. This was completely unlikely as I only fill my vehicle at truck stops when on the road. All receipts have #2 diesel on it and after having a diesel for 10+ years, one knows what they are putting in the tank. Holly's "fix" was to dump my tank, change fuel filter and send me on my way. Within 200 miles, the same issue happened. I brought it to my local Chevrolet dealer, and they pulled the codes showing a bad EGR valve. They reset the codes and ask that I drive it around just to be certain and the same codes came back. the replaced the EGR valve and now my truck is running fine. Holly did "work" that was not needed and further more, put us back on the road with a condition which is extremely unsafe. Once the code kicks, the truck will go into a lower production stage (not run faster than 65 MPH), and then drop to 15MPH. This is a major problem as we were on the highway heading home to SC towing a 40' 5th wheel camper. I am very unhappy with the service and after calls to Holly, they would not do anything. Be very careful using this business. read more