I believe mkengineering are tried and tested its for a r1

is it 4-2-1 ?

and what back cans have people used that will break the sound barrier

Depends where you want the power. 4-2-1 gives better mid-range power, whereas 4-1 will give more on the top end.

If its loud you want, then don't bother with a silencer otherwise go for a universal race can or road legal can depending how loud you want to be

havent you got a yoshi can on yours

so its deff mid range I want 4-2-1

Yep, a Yoshi TRS tri-oval can. It's rather loud.

Best muffler on an R1 for power and sound is a Laser Hotcam by Jama..

http://www.laser-jama.nl/index800.html

No Exhaust sounds better on a bike