A less extreme case is that of the wate-gate controlled turbocharger. As altitude increases, the wate gate gradually closes to make the turbine spin faster in order to maintain constant MAP. This makes it harder for the exhaust gas to escape, so the volumetric efficiency and power output gradually decrease.
Only when the critical altitude is exceeded, and even then, less exhaust backpressure due to lower air density aloft is about an even tradeoff.
The B-36 bomber is a perfect example.
The featherweight versions of this rather unique aeroplane had six 28 cylinder engines and each engine had not only a gear driven supercharger, but
two turbochargers, and could cruise and deliver atomic weapons from 50,000 feet.
The piston engines on this aeroplane were equipped with Bendix pressure carburetors.
Very
large ones.