The RPM drop with smoke is why I was CAREFUL to say set for max smoke at 1/2 throttle, NOT full throttle. And don't feed ANY more oil than that.

Setting for max smoke at full throttle can mean up to 50% power loss at full throttle if the muffler has a marginal size exhaust outlet.

The expansion of the oil in the muffler will create a huge increase in backpressure. you get a loss of power from both: Increased fuel flow (muffler pressure skyrockets... pushing more fuel through the needle valve) and reduced flow in the engine (you have less of the exhaust gas leave the cylinder... and thus less fresh fuel-air mix can get in)

It would be nice to find a way to vary the exhaust outlet size with the smoke fluid flow and throttle setting (and to in-flight adjust the main fuel needle...) but that would be a monster of a setup to optimize...