I didn't read each post in this thread, however, one point is that fuel does three things.. of course, the obvious is that it burns to run the engine.. , it lubricates the engine, and it cools the engine.

Running to lean will cause the engine to run hot and it will not provide enough lubrication.. both of which is how a lean mixture will ruin an engine.

So, the compromise here is to have the mixture just right so you get the proper burn, good power/RPM, and that the engine is sufficiently lubricated and cooled.

CGr.