1996 mustang Gt

I think the '96-'04 forums will be the place to post this

npi heads came on 96-98 mustangs. pi or "performance improved" heads came on 99-04 mustangs. the new heads came with a new cam profile with a little more lift and a new intake with a longer runner and such. you definatly want to use the pi heads if possible, and if your putting the pi heads on a npi motor you will actually gain more power for a few different reasons. the first being all the things i just stated, and the other being that it will raise the compression to about 10:1. tons of people do the swap. it is a 40-60 horsepower increase usually. hope this helps. also if you do a search in the 96-04 tech section there are piles on piles of threads about pi swaps and all that is needed and involved.