ORIGINAL: Bass1
You guys are getting better #s than my Brison with BCM pitts and a Menz 22/8 S prop. I'm lucky to get 6900.
My Brison 3.2 with Slimline Pitts turns the Menz-S 22x8 prop 7200 rpm. Could be your muffler. Try running it open stack and resetting the high speed needle and see what it turns.