I recently purchased a 1999 Audi A6 avant 2.8L v6 and have been having some issues with it. The car I bought was originally an automatic that was engine swapped and transmission swapped to a 5 speed. Driving it around since I bought it, it seems very under powered and stutters sometimes when trying to accelerate. I found a reciept from some shop work done to the car and it said that the engine was from 97 and not 99 and that it was a 12 valve and not a 30 valve, so that would explain the underpowered feel. But I still feel like somethings wrong, any help is appreciated.