How much time do you have on the 580 kit? I am guessing you have had good luck with it. Also, what is Superbike's phone number...I would like to ask about some work but since their website shutdown, I don't know how to get it. I am trying to decide how to hop up my engine. Reason for my asking is I MX race and was up against a stock YZF 450 with the baffle out of the muffler. I was able to get by him but once the guy puts a true exhause and air kit on it, it will be another story. An overbore with a flowed head will be necessary. The track we were at was really rough and I think my suspension did a better job than the stock YZF. I just have rezzies up front and have revalved slightly to my liking after riding. Thanks for any feedback.