i have a 03 pro x 800 is there anybody that have put them in with no problems and have you seen any difference , by the way my sled is stock

You'd be better off spending the money on a clutch kit.

I put them in my xc-800 this fall it seams to rev up a little quicker I dont know about mileage yet the season just starting and I dropped 1 tooth on the top gear (1.64 to 1.70 final drive) power well who can feel 3~4 hp? plus I now have a 1 1/4 track the stock was .91.... by the way if you do get some check the port match from the carb boot to the reed cage, Mine was in need of some light grinding on the reed cage stuffing box! (the little oval white plastic piece)

The people that I know have used them say its not that you gained HP but the throttle crispness is spot on.I feel there costly for what they are .

Response yes HP not that I could tell. There is lots of other add on's (clutch kit) that will give you more bang for your buck
AJ

Well I put 50 miles on my sled today (first time out this year) V force 3's stock motor, stock pipe with slp can, jetted to 440 main raised the needle .010" and change the track to a polaris 1.25 paddle track (not the stock lighting) with 24-41 gears and a EPI pro clutch kit. :div20: I have NO problem pulling the skis of the ground at speeds under 30 mph! are reeds worth it well trottle responce is a must for jumps and getting out of corners quick so ya I would get them for the next sled. I still cant get over how a few small changes make HUGE perfomance gains!