Jan,

What exactly is your setup, did you end up getting the headers? And which MSA kit did you get? Also I'm going to pm you because maybe we can meet up because I'd love to hear how your car sounds to give me a better idea.

And I read it.Some good info,some bad.

Are you saying that on a bone stock(insert L-motor here),that a 3 inch system will work better than a 2 or 2.5?

Yes.

A 3 inch will very likely improve upon a 2 inch pipe, an be on par with the 2.5 inch (diminishing returns). A 3 inch pipe will certainly not hurt performance in any part of the rpm range, contrary to what myths say.

I am doing a bit of exhaust dyno testing on the 20th and will report the results, but as far as the 3 inch pipe comparison, well that's already been done.

Courtesy of zhome.com

There's buggar all difference in those curves that I can see.

Costs and underbody fitment might be the next issues to consider.

Too big an exhaust pipe (not header primaries or the secondary "Y" on 6-2 headers) will not hurt performance. It will also most likely not help performance. Mainly it increases cost and reduces ground clearance.

Bingo, hence why I said you will get diminishing returns going to 3" from 2.5" on a stock L-gata. Fitment and cost are the downsides, not losing performance, as the guys above also realize.

But what about those huge tail pipes I see on wee lil' civics.... there must be some performance gain from huge pipes... surely all those folks can't be mindless, stupid, uneducated, copy-catting, money wasting, idiots? .... or can they?

Some people modify for style (the motorsports lifestyle), others for performance.