I have an 04 DVX with a full Trinity Racing exhaust, K&N, jetted, a 9 setting rev box, power now valve, and a 13 tooth front sprocket. heres the problem, it pulls hard from the bottom end through mid range but flattens out quick in the top end.
just wondering if anyone might have a fix for the problem if there even is a problem.

 

Is it jetted correctly? Have you done a spark plug chop?
When wide open, start to apply the choke... if it increases speed or smoothes out then you need less air, or a larger jet.
If it stumbles or flat spots then you need more air or a smaller jet.
My guess from what you say is that the jet is too big. Thus you will need to get more air or go to a smaller jet.