Can leaning provide more power when running at full throttle?
Yes. The engine will produce its optimum amount of power for throttle setting when leaned to the correct stoichometric mixture.   The primary risk during operation at peak EGT/TIT is of course the high temperature during operation and greater wear and tear. Engines are usually operated approximately 50° rich of peak for max performance or 50° lean of peak EGT for economy operations, depending on the model of engine, flight regiment, etc.  Rich mixtures are preferred to keep the engine cool and minimize detonation risks, but it can also foul the sparkplugs with lead deposits, reducing engine efficiency, power and causing engine roughness during operation.  Excessively lean mixtures can sip gas during cruise but risk fuel starvation or put the engine at a high risk of detonation resulting in severe damage.  For these reasons, the leaning range I stated above is the most widely used.

Normally aspirated engines are often leaned prior to high-performance operations at high altitude‘s, such a short take offs from a mountain airstrip, etc.