What will not change if the prop is cycled at constant manifold pressure is brake mean effective pressure (BMEP), this is equivalent to torque.
I would have thought that the way to increase combustion temperatures would be to increase manifold pressure at constant RPM. This would increase BMEP and temperature within the cylinder.
In other words, assuming the governor is governing (>2000 rpm?) playing with rpm aint going to do anything because the engine isn't going to "see" any change.
Messing with the power level via the manifold pressure (ie throttle) should change things.
Personally, leaning does it for me.
OK all you experts, tear me to shreds.