I know, I was hoping someone around here had put one on, When I look at back issues of MX action and Dirt rider I see that the pro's run them on their bikes, I just don't understand, the only thing I can think is that if you look towards the front of the bike with the cover off, I think that I can see that it ties in with the end of the exhaust port and that if you took at stick you could actually stick it into the exhaust port, this means that the expansion area in that cover must play some role, so I am taking a guess that the flat cover that is put on in replace of the bulging cover reduces that area inside that cover and somehow produces more power, that's my guess at it.