[zr1mom]

On average a good after market exhaust and chip will get you 15 - 25 hp. For the money it's a good bang for the buck before having to add hearders or go inside the engine.

Exhaust alone is good for 5 to 15hp and a chip 5 to 10 hp. You cannot go wrong with a chip from Mr. Haibeck whoo is also one of the most knowledgeable ZR-1 people on this planet.