I think the engine is getting hot and dropping off due to being slightly overloaded. We like to run the 110 at about 9500 peaked plus or minus. Lots of guys run them on funfly type airplanes at over 10000 peak, but they seldom run at full throttle for long periods.

I would put a little lighter prop on it and let the engine breath!

Glad she's running well.

Good Flying!