Q about slip-on

[Amber Lamps]

Originally Posted by DLIT

That or it can be because you still have the cat on there. The stock muffler has no silencing feature at all. I replaced the cat on my '09 r6 and kept the stock muffler on and my bike's loud as fuck now. The cat does most of the silencing, this could add or be the reason why it's pretty quiet.

Yea you're probably right, I called it the "under" muffler... Did the '07 have a converter? What I do know is that there is an insert that can be removed in many Yosh models. We did my buddy's GSXR600 last year and I almost begged him to put the silencer back in! OMG fucking loud! Like you said, we removed the muffler/exhaust tip and the "under-muffler" on muffler/converter combo. Anyway, before anyone breaks out a fucking drill, they should first determine what model slip-on they have (wasn't mentioned in OP) and give Yoshimura a call!