Originally Posted by Lion BR
Watch out, the left side (viewed from the back) is the catalytic converter. At least this is where it is on mine (2006 model).
That's right, but cat is only in the header end of the can. Logically I can't see any reason why opening up that end cap would not convert it into a proper exhaust with in-built cat. It'll possibly be very loud because it may not have a baffle. All depends on the internal ducting inside. I'm hoping the internals are very similar to the older pea shooter design.
F650.com Pea Shooter Baddle Mod FAQ Write-up
kovrob may have the answers.