I've used Scorpion cans on mine. Look the nuts, sound the nuts, fit well and the after sales service is top draw. (I've destroyed 2 of them, took the cans back and got instant replacement with no questions)
The only complete system I would recommend on the M4 system. This is what most of the racers use. Having said that I've not heard much bad said against the o/e system. Is ok up to 75-80bhp - but to get these figures out of a 650 requires a lot of work...
JHS in Keynsham are very good, have a chat to them.
