Sorrow,
M-82FN fuel injected engine replaced the M-82F on La-5 production lines at late march 43, continuation war ended at summer '44. G2's were used to the end (and after that) by FAF. I bet they met in the air. And the result was very one-sided, and not in favor of the Russians. In spite of the fact of Russians having huge numerical advantage.
Maybe you are mixing things up with the metal-structure La-7, which replaced the La-5 in production late '44?
One thing about explosives and ammo. If you compare only the energy contents of explosive charges, you will get seriously mislead. There is a property in explosives called brisance, and that determines many of it's destructive capabilities much more than the thermal energy produced. For example, the velocity of a shell fragment does not depend much on the thermic energy, but is almost totally dependent on the velocity of the detonation wave (ie. brisance).
There is all the difference in the word between same weight explosive charges of amatol (mixture of ammonium nitrate and TNT), TNT (tri-nitro-toluene), pentrite (maybe penta-nitro-toluene), hexogen (hexa-nitro-toluene), and octol (octa-nitro-toluene), though I am almost sure no-one had octol in useable quantities during WWII.