I have a 2000 Yamaha TTR 250. I am 14 and i have had the bike for 6 months now. The bike has a Stroker SX-1 muffler on it and that gives it better acceleration. I have been looking for aftermarket parts and I have narrowed it down to a few. I can get a racing cam for $275. I can also get a wiseco piston kit to take the displacement to 263cc for around $120. I can also get a header for $120? Finally I can get a 325cc big bore kit for $530. I have been having a hard time making up my mind on what would make the biggest difference in throttle response and torque. If you have any helpful suggestions please post the. I am not limited to only one of the above. Thanks, Trevor.