ok from the people i have talked to evo engines are far from the best.
i dont own one. you want a response so im giving one, take it w/ a grain of salt
check your idle, to lean?
also you may be either to rich or to lean on the HS needle. set it way rich then transition to WOT. at the same time start leaning it out.
i have a magnum .40 that would do the same thing your stating. did the above to find the actual HS position.
also that prop may be a little big for that engine, try a 10x7 to keep it running cooler when breaking in