Exhaust thrust is dependent on the mass of the exhaust, weight of the air +weight of fuel+ weight of any additive (Nitrous or MW/50) times the velocity of the escaping gas. Velocity of the escaping gas is dependent on the preussre in cylinder After teh exhaust valve opens ( to some extent), The shape and length of the exhaust pipes, the size of the nozzle opening at the end AND the atmospheric pressure at the end of the pipe/nozzle.
That gives you the thrust but not the power. Power varies with the speed. The faster you go the more power you get from the same thrust.
For similar engines in the same air frame a lot of the variables get very close together.
However something to consider is that the weight of the fuel/air is the weight needed to run the complete engine, Friction and supercharger (one or two stage) plus shaft horsepower.