ORIGINAL: jeffie8696
It sounds as if the high speed needle may be too lean. You say the pinch test but do not elaborate. I find the pinch test unrevealing for the high rpm setting but very useful for the idle mixture setting.
I find it odd you dont see the pinch test as being revealing. Thats how I set nearly all of my engines, and have a tach as backup. If anything, I find a slight rise in RPM on the pinch at WOT to be 500-700rpm rich instead of the typical 300-400rpm rich most people suggest/use. I dont use the pinch test on the idle needle though, as I rely on the transition quality as the determining factor.
Hmm... Thats just me though.
As to the OP, if you have a tach, you should tach the engine at WOT and see what rpm its turning. 7" and 8" pitch props are pretty high, and chances are that high pitch is lugging the engines down too much. Try a 5"or 6" pitch instead, and re-tach the engine.