Some more Byrohints...
Don't bench run the Byron setup, and don't run it hard for too long in the plane at full bore. There is not enough airflow over the engine to keep it from getting hot with the pusher fan.
Run two rich tanks through on the ground, then go fly.
Get an inflight mixture valve. I feel it is NOT optional. It's a lot cheaper than a new $160 91 piston and cylinder from one lean run.
The 91 is the best engine out there for Byron.