Is HPT or another tuning software necessary to flash the PCM back to stock? The GTP that I picked up has a modular 3.4'' pulley, and I just picked up a modular 3.8 to take it back to stock. Right now i'm just trying to get it road ready and reliable, as there are no other supporting mods for a 3.4'' pulley other than a PCM tune. and the only reason I know that it is tuned is because the fans stay on after the car shuts off. Eventually i will go back to the 3.4'' pulley, but it is a little down the road.
Thanks,
matt