This is a bit messy so I`m not 100% sure whats being asked - however I think it would be instructive if I shared whats called a "mixture response curve"
This was developed for aero engines in the late 1930`s, and was at least published first by German engineers (this is not necessarily proof of others ignorance on it).
The mixture response curve was the fuel chemists creation after they started realising how worthless the Octane number was once you get down to very detailed development, because the Octane number (pre about 1942) was done at ONE air/fuel ratio, ONE engine speed, ONE air temperature ONE ignition advance. It didnt take long before engineers realised that if you vary those parameters, the detonation limit (analogous to the Octane number) jumped around all over the place, and in certain circumstances some engines made LESS power on fuels with higher octane fuels (once you get down to looking at differences of jus a few points).
So they decided to measure knock resistance across the full range of air/fuel ratios and make a graph (a more primative version of this is what the Allies essentially did when the 100/130 PN grade fuel specifications were jointly agreed between the UK and USA, which measured octane at TWO air/fuel mixtures not ONE, hence 100 Octane lean/130 PN at rich, its essentially the same fuel as 100 Octane from 1940, just measured with greater diligence).
Germans being Germans decied that a couple of points were no good, they wanted a complete curve, so they measured it at perhaps six or more points.
An example is below, in short you can make a LOT more power at rich mixtures for two reasons, firstly the cylinder may be kept cool by the extra fuel (a lot more than
can actually be burned, potentially) which raises the knock limit so you can increase boost, and secondly you can obviously burn more fuel because there are more
fuel carbon and hydrogen molecules floating about inside the cylinder to combine with oxygen.
Of course, if you have an air cooled engine it may be advantagous to run at a rich mixture a lot of the time to help keep temperatures down, which is a reliabilty factor,
but this doesnt mean that you CANT make a lot more power at rich mixtures if you are able to do so.