when i did the 01 pcm in my regal i did it in the car, and then it went into the compatibility mode window, then i had to pick a years and engine combo that matched my car. and it went fine.
that compatibility window has not come up on the off board. nor have i been able to make it open up again. so im thinking when you switch a pcm with non matching part numbers it should be done in the car.
maybe if you put the pcm back to the 99 bin, then try to flash it in the car, it may work better if the compatibility window opens up.
