ORIGINAL: Charlie P.
Almost every prop plane in WW2 had a method of adding 20% or so for those times when it was desireable; whether it was a wire that could be "popped" by forcing the throttle or by blowing water into the cylinders. There are times when a little extra "oompf" is very, very nice to have.
Charlie - that power setting was called "War Emergency". My dad flew P-38 photo recon out of England during WW-II and he said thatpower setting saved his life more than once. Total armament on a photo P-38 was a 45 sidearm that the pilot wore. Other than that he could take your picture.
He said there was nothing like sitting between those 2 engines and shoving the throttles forward and hearing them scream into life. FAST!! Especially downhill. Photo recon planes also had NO escort planes. They were on their own.