Does any one know of such a mod:
http://www.joinbike.com/bbs/viewthre...extra=page%3D1
also at http://www.joinbike.com/bbs/viewthread.php?tid=325985

It is a simple mod by enlarging the front and middle sections of the muffler from 34mm to 42mm. The guy who started it claims that it greatly improves the performance, sounds better and increases the top speed from 150kmph to 165kmph. The shop plans to produce them in volume.
Does such a mod make sense and possibly achieve the performance boost as claimed?