Ive got an 04 grand prix with the flomaster exhaust, rims, system and such but its still lacking the performance part so ive been looking into doing a swap from the stock 3.8 to the gtp's 3.8 supercharged engine. Has anyone done this or know whether or not itll work? And if not do you kno what engine which work? thanks.

Why not just add a S/C to your 3.8? Probably be quicker than the stock 3.8 GTP S/C engine anyways!

probably true, but main thing is to check on the specs to see if you need to replace any other parts with that SC....i'm sure you don't want a blown engine

The engines are quite different but you can do it. There is a kit but you need LOTS of gtp parts.

https://www.zzperformance.com/grand_prix/products1.php?id=382&catid=109

Depending on your budget...I'd just bolt on a turbo kit. Better gains and more efficient than the M90

don't forget that the trannies are alot different as well. gt trannies are alot weaker than the one that comes with gtp's.