What prop are you using on the engine? Brand of oil and ratio? Reason I ask is I've had a very good experience with the BME, but was careful to do everything by the book.
I'm running a 22x10 now, and I'm on the fifth gallon, and going to synthetic oil after this gallon.
I can tell you straight up the things got power, and just keeps getting more powerful. Sorry to hear yours is having situations.
What kind of RPM readings are you getting on the ground?
Brand new first 10 minutes of it's life I got 6300r's, it slowly crept up and is now at 6700 to 6800 with 22x10. I ran it on the bench though for about an hour before installation, carefully monitoring time and heat, with the first few runs being 3-5 minutes, increasing time every run, until I could comfortably run a tank empty...it only took about 3-4 full tanks and I had no question it was ready for the plane.
Also..something different from glow is, the tank vent does not go to the muffler! The tank vents out of the plane wherever you can get your vent line decently routed. So the tank vent is always open. Just route it up,,,then down somewhere, usually around the firewall area.
Then I did just as dick hansen is telling you...vary your throttle positions, to get a full range of RPM's.
Airflow is very important too...is your engine cowled in? If so, is there adequate ventalation? Meaning air in....and air "OUT" . Reason I ask this is I've seen installations that are beautiful from the front, but offer little to no escape for air that comes in, hence...no flow.
You should have as much or more area for air to escape the cowing, as you do air-entry. So that muffler exit and even other parts of your cowling, should really be alot bigger then your air entry-way to offer the flow.
Another suggestion is to pull it out of your plane, take it back to the bench and run some tests on the bench, pretty much as we've said here. This way you won't endanger your plane, nor your engine. It's alot of $$$, and you might want to be sure. Starting over kind of.
I do hope this helps...look forward to hearing from you.