Chuck
If you find that you get no drop in power or an increase in power when you apply carb heat, that is a bullet proof indication the thing was to lean...hot air is less dense therefore hot air enrichens the mixture.
Is this really true?
The reason carb heat application reduces the engine power (shown by an RPM drop on a non-CS prop engine) is that the air is warmer, which reduces the efficiency of the engine.
The operation of the carb, or the fuel injection unit, should reduce the fuel flow approximately correctly to maintain the air/fuel ratio.
(I say "approximately" because both metering systems measure a mixture (no pun intended) of volume flow and mass flow when it comes to air, but they do measure mass flow accurately when it comes to the fuel.)