What kind of a muffler are you using? I used the Keleo live stacks and the following:
Safeway 87 Octane fuel, Lawnboy 32-1 oil, about 85 degrees, and a 3W 22-10 wood prop, got about 6000 rpm. First gallon of fuel. With a Zinger 22-8 three blade prop I got about 5400. Switched to Safeway 92 octane and saw about a 200-300 rpm increase. Please keep us posted!
Sam