Rear engine power loss during flight

[Mich3773]

The situation you described while taxiing off the runway is normal. It illustrates the typical rear engine cooling while not in flight.

After landing the engine is hot. Even with the rear cowl flaps open there is not enough airflow over the cylinders to reduce their temperatures. Cylinder head temperatures normally increase. Slightly low oil pressure is the result of hot thin oil and low oil flow rate while taxiing. Normal oil temperature is the result of a the oil cooler oil pump continuing to remove the excess heat accumulating in the cylinders.

Loosing rpm in cruise flight ... Prop moving but not cranking ...Hmmm .... sounds like you made a good decision to land immediately. Please let us know what you find.