Eagle Flyer, How far out is the main needle on your TT91S? Unless they did some refining to the needle assembly it should be around 5 1/4 turns out. You should be getting a 1000 more RPM with that prop and fuel. Check the timing and valve clearance.
Is your engine thoroughly broken in?
Putting a piece of fuel tubing on the needle seems to help seal it with it being out so far.

Those Prince Am. planes sure do look sleek. I'm glad to see some info being posted about them.