Sounds like your mixture is too rich.

Start with setting your high-end mixture first - lean it until the RPM peaks, then back it off about 4 clicks rich, or about a 400 RPM drop.

Next start leaning out the idle mixture about 1/16 of a turn at a time and see what it does. You'll find that when you make a change to one mixture setting it will affect the other, and on some engines it just takes a bit of tinkering with them before you have everything dialed in.

Hogflyer