With a correctly jetted yz250, you really wont need mods. You do realize that even the top ameture riders that are about to enter the pro ranks, rarely use a bikes power to it's full capabilities. I can promise you that if you learn how to keep in the power and learn how to stay wide open through turns, you will not need more power than a 2-stroke 250. If you have too much power, you will never learn how to ride correctly. All that will happen is you will putt through corners, then try to catch up in the straights. Just get a close to stock 250 smoker, then learn how to ride it to it's potential. I promise you that even with a full blown factory 250 smoker, a kid in the top of the ameture ranks on a 80cc smoker will leave you and never see you again, that is until he laps you. It's all about knowing how to use it....