[skyking]

Good point! It is along the lines of TANSTAAFL, that air moving through the body is indeed subject to drag. He won't just be using exhaust, he has cooling air needs as well.

I have had a few Cessna 310's, and the early models had an exhaust augmenter system that used the exhaust in a venturi effect to draw cooling air through the nacelle.
Every other twin engine had cowl flaps to control cooling air, and the early 310's did not.
Different power settings would provide the necessary change in cooling for the aircooled engines.
Read here about augmenter systems.
Exit Area Too Small ?????? - Page 7 - VAF Forums

4th plane down is a B model with overwing exhaust and muffler, augmenter.
https://en.wikipedia.org/wiki/Cessna_310

Later models used underwing exhaust and still had an augmenter, until the last few models or the factory turbo planes which had drag inducing cowl flaps.