What do I need to be looking at when managing my mixture

When I lean my mixture I just try to find highest rpm’s.

Quote from MrWingFlex

When I lean my mixture I just try to find highest rpm’s.

You will fry your pistons

Don’t follow my advice! What are ways to properly lean your mixture?

Quote from MrWingFlex

When I lean my mixture I just try to find highest rpm’s.

You could do that in a plane with electric constant speed propeller/s (or with fixed pitch prop/s) as you can turn the electric operation off. In that case tweaking the mixture will slightly change the engine rpms. So it would work in the P-38.
Hydraulic constant speed props would instead change the pitch and engine load so that method would not work, they need monitoring of the exhaust gas temperature and fuel flow.
A small margin on the rich side prevents engine damage especially with descents where increasing air density leans the mixture.

This is not simulated in Aerofly to any level of sophistication.

Quote from WAR_Capybara

You will fry your pistons

Aerofly pistons are virtually indestructible unless there's a bad update 😂