Very good point. I'm sorry I did not mention that up front.

When ever you suspect an engine problem, put the engine on a test bench. If the problem is with the engine, rather than the installation, it will be evident pretty quickly.

Running at 7500 feet will cause a drop in output power, but should not cause overheating.

If the engine is indeed running rich, and there is definately visible un-burnt fuel coming out of the exhaust, and it is still getting hot.... there is an internal problem with the engine, such as the bearings, bent crank, bent rod, distorted piston, or peeling liner as had been mentioned earlier.

The 'popping' noise you discribed is unusual. Have you disassembled the engine in the past ?

My experience over 28 years has been that 85% of suspected 'engine problems' are traced back to the fuel system or engine installation.