I hate the wrong data in Il2 strmovik 1946

[Furio]

More weight equals more angle of attack to stay level, and more alpha means more drag. In fighters this is less evident than in bombers (think of B17 speed with load...), unless there is a significant fuel load, as is for long-range planes.
I don’t know how much this is modeled in game. Surely, trim, mixture, prop pitch, supercharger speed and radiator shutters position all have a BIG effect.