[Jack21]

Gut tells me retarded timing. Fuel charge being ignited too late producing more heat, but less power. To compensate, you're adding more fuel (which makes it worse) when you should be advancing the timing. Initial should be 12 - 14 deg, with 20 deg centrifugal all in by 2300 - 2500 RPM.

If you're using a hydraulic roller, look for 15 - 16" vacuum at idle.

You should be able to hold your hand an inch or two from the coated header with the engine idling, and it should feel warm, but not hot so you'd have to pull your hand away.