03 still is a series 2the motor should work 4 a even swap... no changeing the pcm you should run the 98 pcm and should look for a differ maf and tps that is bad... i am 99% sure on that one....
Bottle feeding a GTP is the cheap way out
the only reason i dislike nitrous is because you can run out of it. otherwise if you were to have a lot of money on a bet, youd be a damn fool to not throw a bottle in the car.