Exhaust Question
 

Would adding a custom header to a high-flow cat system help performance, or just waste time? I have a Pacesetter header at home from my previous car, and I'm looking to get a high-flow cat system like the one I had (Bonez), but the length of the header is too long. Just wondering if it would be beneficial to shorten the header, retain the O2 sensor bung, and attach it to the cat system; or is all that work just not doing anything more than what the OEM manifold attached to the high-flow cat system can do?

I know you're all thinking, "Dude, just go straight-pipe" I did that with my previous car ('87 N/A) and it sounded badass with the header and mufflers, but did not run very well. I want to keep cats for CA smog reasons (regulations actually...I could care less about the pollution created from one RX-7) as well as actually being able to pass the strict standards here. Thoughts? Comments? Thanks!

-Bryan

There will be a negligible power difference by using the stock manifold over the modified pace setter header.

im sure adding your new exhaust and retaining the cat would still increase power, it would also sound better. One thing to remember is the 6 port works with back pressure to open the secondaries. You need some back pressure to open them. Better yet with all those miles read up on a rebuild and while your at it port that thing.

Yeah, I am keeping the 5th and 6th port actuators in mind, which is another reason why I don't want to go straight-pipe from header to mufflers like on my previous car. I am also planning on a rebuild for this engine, but not until the thing craps out on me. I have read procedures on how to port it and stuff and will likely do it while I have the chance WHEN I get to that point.

Thanks for replying. I figured there might be a chance that the hp increase would not be significant even after I severely modified that header I have to fit with the exhaust system I have planned, but I wanted to hear it from you experts first :)

Don't bother with the header...... thats my thoughts..... not worth the hassle of you are keeping the cat

Correct me if I'm wrong but I didn't think any porting of the engine would allow your car to pass CA smog laws. You seem to want to stay legal so I might be careful of that.