On the contrary; I find it very interesting that the Hungarians managed similar S/L speed with about 600 hp less... Can you share the source of that info?
Sorry for the late answer, i didnt have net for a couple days.
Unfortunately only rumours in the hungarian flight simmers community (mostly il-2 tho)
During the era of the communism, everything from before 1945 was destroyed, maybe thats why i couldnt find any factory data.
There are books written by emmigrant pilots, mostly from the old 101st "Puma" fighter squadron, the rumours are usually referring to those memoires.
Yup, Sir, im not a reliable source

All i can say, that "600 less horses" is still 2950 in a 17-18000lbs aircraft, if that makes sense.