It would be nice to see power differences between options, some dyno results for the primarily offerings. I do not entirely trust manufacturer provided power info, which they are not even providing yet. With a slip on, basically, a 2" hole is a 2" hole. But it is reported that for the GYTR offering (I think it was), the length does matter and makes a noticeable difference. Louder does not mean more power. Riding last night, I was thinking the Yosh R-77 is almost too loud for city riding, in the canyon or track, I do not mind it at all.