Having an issue with my 427 after dealer installed new exhaust studs. The first time they started it, it blew an injector. They rebuilt injector but it only lasted 3 hours. Replaced injector, no power and engine sputtering.replaced all 6 injectors, no difference. Then dealer decided computer has gotten antifreeze in it from coolant sensor so they replaced harness and ecu. No difference. Got a super hot program from mack which actually helped a little, but still no power and low rpms (1200 to 1600). They checked epu's again and felt that #5 was bad so replaced it. Nada. Got 3 more data files from Mack..Nada. Mack said replace turbo. Made slightly more power but no fix. Truck tach actually goes backwards when taking off. Like the motor is surging. Now what?