Looking at this graph I see that a piston engine provides less than best power when the mixture is richer than best power, and this is expected indeed.
I know that at full throttle, more than the required fuel is provided to the engine in order to achieve better cooling. Also, I know that - especially on supercharged engines - the amount of "cooling" fuel is quite high, that is, the engine is not surely providing its best power when at full throttle.
If an engine is rated 300hp when at 29 inches of manifold pressure (MAP) and 2700RPM at full throttle, does it mean that it is actually capable of providing more power if leaned to the best power mixture? It seems to be that it should be able to provide around 8-9% more power. Of course, I would expect it to suffer some serious damage.