What could excessive lean mixture under a high power setting potentially lead to?

Excessive leaning of the mixture at a high power setting can lead to detonation in the engine. When the air-fuel mixture is leaned too much, it can result in a combustion temperature that is higher than normal. This elevated temperature can cause the fuel to ignite before the piston reaches the top of its compression stroke, which is known as detonation. Detonation is harmful because it can lead to severe engine damage, including broken piston rings, damaged cylinder walls, and stress on engine components.

On the other hand, while leaning the mixture can sometimes improve efficiency or fuel economy, doing so improperly at a high power setting poses significant risks. Enhanced performance might be experienced, but only within the limits prescribed for engine operation; leaning the mixture excessively at high power contradicts safe operational practices.