as far as hp gains.. you will gain almost nothing. to get gains you need to complete a whole exhuast system, I/H/E. It's like buying nike shoes for a fat person. you need a few more things or else no gains.

This link gives you a preview of certain exhuast.
http://www.team-integra.net/sections...?ArticleID=451


the sound quality doesn't sound that well, the best way is to go to a track and ask people to rev for you. I've got a greddy EVo II, I love it, no one has ever said it soinds "okay," it has always been it sounds "awesome."