350 Odyssey won't rev

My 350 runs great until about 50% then seems to sort of 4-cycle. If I hunt a little I can find a "sweet spot" when the motor seems to run a little better and a little higher rpm. If I push it beyond that point I get minor coughs back thru the carb. Anyone have a clue what is going on?

there is a rev limiter connected to the neutral switch. To check it you have to disconnect the cable above the battery box and ground it out

Sounds like the carb adjustment