So much goes into the header design and exhaust that most do not understand. It's all physics, with sound waves and interference and on and on. Camshaft timing and header length and diameter have a huge interplay, and I doubt that stops at the header. If you want a good read on exhaust tech, go to
http://www.team-integra.net/section...cles.asp?Show=1
and scroll down to the exhaust section. There really is a ton of very valuable info there, so check it out. Don't worry about the fact that it is an import site; remember, those guys are getting stratospheric specific output.