Just slapped a Big Gun Rev Box into the 450 and it does make a noticeable difference in overall performance. In fact, I'm not sure the beast really needs that much HP. What am I saying? Anyway, being the only thing that I changed, and BG not providing any tuning/jetting/whatever tips (nada) with the unit, I'd have to say that installing the Rev Box has made it extremely difficult to start. Like they bumped the initial advance a little too far? Warm or cold, fast kick/slow kick, full kick/short kick. It just won't start until your leg is about to fall off. Any suggestions?