Don't forget to check the valve clearance while you're at it....

Also, there can be some differences in tach readings depending on who's tachometer you're using. I finally went to a TNC tach as I was getting different readings from, shall I say, less expensive tachs? Now I'm not pushing that particular point here as my 110's will haul a 9lb. model around with authority so the fact that you're having what you think are performance issues with a lighter model would suggest your tach readings may be close. Just a thought.

I've never tried an MAS prop but from my experience with the GS gasser stuff, props can make a tremendous difference on those models and you pretty much have to try different manufacturer's and sizes to get a suitable prop for your particular flying style and a particular model/engine combination. Also, going from 20% nitro to 30% yielded more RPM and a slower idle with the engines being a bit easier to tune when I did the fuel change. You should, I think anyway, be able to notice a difference between the two different fuel nitro levels.