06 KTM sx125 power valve

my sx is lacking alot of power. bottom end is okay. no top end. no power band. on the track im pinned 50 percent of the time. clearing jumps is a challenge. i bought the bike from a woods racer. i assumed it was the flywheel. but it has the stock flywheel. i assumed it was the timing plate. but the lines are matched up. its not the pipes either. the power valve only moves when in high rpms. and seems delayed when cracking throttle. any other suggestions on what it could be? im thinking the p-valve. and it isnt snappy like a two stroke should be. no snap at all. HELP!