In my experience, "lead deposits" are basically an issue caused by running excessively rich mixture, usually on the ground, and show up as spark plug fouling wi

In my experience, "lead deposits" are basically an issue caused by running excessively rich mixture, usually on the ground, and show up as spark plug fouling with engine roughness and reduced RPMs. The fix is just to vaporize the deposits by running the engine at leaner and at a high power setting. I understand that you can also end up with exhaust valve deposits, but that's not something I've seen personally. Aviation engines (especially those used for training, which is a large proportion of the piston fleet) have incredibly short inspection intervals in any case.