The real P-38 easily outturned any fighter Germany produced in the war.
The Germans had essentially only two fighters. The bulkier Fw190, in the game, is easily outturned by any P-38. The lighter 109, less than half of what the P-38 weighs, with a more favorable power loading and smaller wing loading, has a much smaller turning circle than the P-38. But many P-38s are davantageous in instantaneous turning capabilities which often makes it more than a match for a 109, especially on the offensive vertical, not to mention the later Bf109K-4 is thoroughly outturned by the P-38.
So we've got the in-game P-38 easily outturning more than 60% of in-game German fighters, on par with at least 30% of them, and decisively outturned by only the earliest two models of 109s, the E and the F.
So how is this supposed to be "modelled wrong" again?
and each engine was capable of about 2,000 horsepower.
Each engine was also capable of adding more weight to the plane, no?
So try pit the 17,000lbs of P-38 mass with two 2,000hp engines, against a typical single-engined fighters with a single engine rated at 1700~1900hp, weighing in at about 3,000~5,000lbs. Is it any wonder these lighter planes climb faster, turn better, and accelerate better?
Ground crews regularly set the engines to ratings in excess of 1,800 horsepower.
The same could be said for a lot of other fighters as well. AH modelling sticks to published data for all planes, not just the P-38.