1994 yz250 sputters as soon as i hit the power band. are my reeds causing this?

i recently bought a yz 250 it starts first or second kick all the time and has great low and midrange power but when i want to wind the motor out in the power band it sputters like its to rich as soon as i get in the power band. i have been all thru the carb cleaned it rejetted the whole nine yards and still nothing. the only thing i havent done was change the reeds i looked at them and they had a gap at about a 1/16 of an inch so i flipped them and it still does the same thing and i also installed a new powervalve being that the old one looked like it got in a fight with a piston at one time but it was rebuilt since then and i did check the piston and cylinder and they look like new the comp. test checked out 185lb so i know that isnt it im clueless rite now except the reeds but i didnt think they made that big of a difference. i just need some input on what i should do. thanks