I picked up some Akrapovic race exhaust cans (with the ‘y’ connecting tube) from a friend of a friend who sold his R1 last year. They sound absolutely fantastic! You do get a small horsepower gain thanks to improved air flow but the main reasons for these are sound and looks. I was in two minds about fitting the ‘y’ connecting tube, which replaces the stock pipe which has the catalytic converter in it. According to Akrapovic, without it you get slightly higher peak power, but fitting it improves the general power curve so I opted to put it on. Pictures are here.