I hope you don't mind an "outsiders" post, I think that I may have some interesting info. The Michigan Cycle Conservation Club did some testing of the CRD quiet exhaust on the XR400. Yea, I know, the XR is not the most performance oriented bike BUT.....the 94db stock exhaust note was reduced to 83db!!!!!! Seat of the pants riders (a lot of them with a lot of experience) said that there was a slight performance gain. Here's a web site you can find more information on them www.ligneracing.com/html/performaquiet_pipes.html I've heard the "uncorked" WR's in my riding area and I know you guys need some help finding a good pipe that doesn't kill the power! Sorry I tried not to give any digs !