[Frostbite0180]

Looking for some advice on how to approach my current exhaust problem. I am current running a K-tuned slip fit racing header (4-1 i believe) to a Invidia Q300 catback exhaust. This is all connected by some POS test pipe with a slight bent flange that is currently leaking. I'm wanting stock level noise and would like to have a Cat to get rid of that awful smell. However, I don't want to loose the performance of a performance header, as I am planning on rebuilding my high mileage k20 for some NA power. Anybody have suggestions? I realize I might be asking for the impossible, but how can I at least get close to my goal?

 

[dopeyrsx]

I would fix the leak and call it a day. If you want it to quiet down, you can add a high flow cat as compromise but still won't be stock quiet.

 

[IronGumby]

Fix the leak for one. Easier said than done. I actually spliced in a hacked down 2.5-2.25 adapter cut at an angle to slip fit into my testpipe from the collector. It helped but I need to get a welder friend to fix the alignment issue with a real elbow. Leak noise trumps anything else you do.

Secondly, if you have aftermarket/upgraded motor mounts, you can get back on the cabin noise/vibes inside by swapping out the passenger/engine mount for the stock oem one to quell the sound.

Thirdly, it's funny cuz some people say the Q300 is quiet (some upgrade to something louder!) but in my book I'd think any 2.75" exhaust would be quite loud. 2.5" (65mm) offerings would get you closer back to stock levels, or especially 2.38" (60mm), but that will kill your NA goals.

I'd comment on your All-Motor NA thread but I'm a n00b in that department. I'd be interested to see though if someone recommends you try >12.5:1 compression pistons and forego the frank route because be prepared, almost everyone will tell you frank it to achieve your goals