I only have enough for one or the other, either the header from chevy or the cat-back exhaust from them. Or i was thinking a header and maybe a bolt on muffler if any one has one, but I can't find one. Please give your advise. All I care about right now is power.

 

exhaust will give a lot more power than the manifold will

 

I would say the cat-back for right now.

 

GMPP cat back FTW