Your making it too hard.

Mix up your oil and fuel. Don't use some rediculously lean ratio like 100:1. Mix it up at 40:1 or 50:1.

Tune it and Fly it.

Checking your head temps while it's sitting on the ground running under a heavy static load is NOT going to give an accurate reading. Thats completely different than the temps when it's moving through the air.

If it ain't broke--don't fix it. Put oil in the fuel and fly it. There's been a zillion G23 engines run long before you and I were flying model airplanes. Not too many of those guys had infrared temp guns. They just went flying.