The best motor mod I ever did to my 99-02 KX 250's was the installation of a flat top piston with the head mod done by Tom Morgan. Jay Clark, a former Wiesco rep gave me the head and Piston one year at Mammoth Mountain MX, he guaranteed that it would be the most impressive 250 I ever rode, he was right. I never tried it on any of the newer 250's, they seemed to be pretty impressive as it was. OK, now having said that, I don't really think you probably need more power, what I suspect you need is a means to use all the power you have, and to do that the first place I'd start is with the suspension, and who you chose is up to you but in my experience you ar better off to chose some small shop, if you go to one of the big houses and don't have a reputation you get the standard stuff that everybody gets, or maybe nothing at all but a big charge. I sent suspension to Enzo, cost me $800 got it back and my son complained that it was to harsh in the whoops, called them and they said it was perfect he was chopping the throttle in the whoops, so after 3 of these calls I tore into it myself to find that the valving had never been changed the peening on the shock nut was never ground off, called them again only to be told that I was basically full of it. So to this day I never reccommend Enzo and recommend that nobody sends there stuff to them.