Rep Power: 238

You're still spouting this crap? Seriously... say it with me... SCAVENGING VELOCITY. Back pressure does not matter at all. Remove any idea of back pressure you have in your mind. A well designed aftermarket exhaust designed for maximum power will give you good gas mileage as well. It all depends on driving style. A turbo car can get great gas mileage too if you keep your foot off the floor.

 
Rep Power: 208

What ever happened to tuneable tips? I used to use them on my old VW's and seen them on some newer cars also. What happens if you put a tuneable tip (like a supertrapp) on a high flow exauast (header+cat)?

 
Rep Power: 812

i remember seeing a nology tip with a gated door on the end (with holes) that would stay closed at low rpm and open up at hi rpm when the exhaust was moving fast enough to open it. not sure how well it works, and it was very ugly looking. the newer rsx type-s (or was it type-r?) had a chambered muffler design that had a similar concept of accounting for lo and hi rpm driving. i think there was a valve or something that opened up at higher rpm.

 
Rep Power: 208

This is actually what I was talking about...

You adjust the backpressure by adding/removing plates. I had one on my old dune buggy.