[Gaz64]

I would think that the engine is still richer than stoich, which it should be especially at 6500 rpm.

If it was lean, the engine would be down in power, and lean is high oxygen, all the fuel is consumed and no further combustion occurs.

I would be looking at the ignition timing is late (ie: 30 where the engine wants 34), for the power produced.

Combustion is then still occurring while the exhaust valves are open instead of almost ceased, and the exhaust runs hot.

What induction system is on your motor?

Can you have the whole second half HPC coated, after the first join, collectors, muffler, and turn out as an assembly?

I've seen brand new HPC coated pipes glow red in the dark, then return to normal finish once they cool.

Many engines have glowing pipes under heavy load.

Gary