Ive got a b20v currently has a stock gsr exhaust manifold on it. My buddy has a ebay manifold that hes gonna give me but which one should i use? Is it even worth my time to replace the one i got.

 

which "ebay" manifold are we talking about? a 4-2-1 or 4-1? what size collector? type r replica? well almost anything aftermarket will be a little better than the stock gsr exhaust manifold.. just make sure that the one he has is also for a gsr or you will have to modify the rest of your exhaust so it can bolt up..