Originally posted by pythonscott
I agree with replacing the cat to a high flow, but I disagree that a 2.5 catback exhaust needs to be used (though it wouldn't be a bad idea) and here's why: the exit on the JDM collector isn't really 2.5... it's more like 2.25 and the A-spec header exit is around 1.75. So using a 2.25" cat back really doesn't create a bottle neck like you'd think it might.
I highly recommend going with a J-spec header. It will give you a signifigant power increase, while like snoopy said in his first post, an A-spec header wil only net 2-5 hp.
To answer your question of which header is best, HyTech and SMSP are. And yes, they are worth the wait and money.
Thanks dude, and to eveyone elses advice. So I guess I'll keep my 2.25" piping -thats good news. I want to beable to switch to my stock exhaust mani when I get it smogged in 2 years. F_cken California!
Do you guys know if most of these 4-1 headers are easy bolt-ons to gsrs? Because like I said, I need to beable to remove it easily for smog.