I have almost EXACTLY the same mods as you and I installed the 440 kit from Thumper. Made a big difference,,,,not the "big difference" that everyone talks when you put the pipe on,,, I done my Yosh full comp with jetkit and filter and it felt the same to me,,, like it added 0 horsepower,, until I raced someone that I used to run equal with before,,,could I tell the difference,,and then it was only 2 bike lengths faster in a standing start to top of 5th race,,,the 440 kit was a NO QUESTION horsepower enhancer,,,muchmore power. I have the 440 high compression piston and sleeve for sale,,,I JUST took it out today,,,it has approx 12hrs on it and looks great,,,,,based on the way it looks,,I'm saying less than 12 now. I'm going to the bigger 470 kit,,,not that the 440 isn't enough,,but I'm always looking for more power and ready to step it up some more. I originally said I'd take $170 for the set up (piston,rings,sleeve) but after looking over my paperwork,,, I'd be to close to giving it away at that price,,,the first person with $200 gets it. Check out the pics at this link
http://photos.yahoo.com/bc/jster171/lst?.d...ol+pics&.view=t
The ones I took today are pretty obvious,,, dirty piston and the sleeve pics are titled "for sale" I think.