My experience is that with less than 40% fuel the P-51 can even out-turn the 109K in a flat circle. I reduce the default fuel load to 30% usually (sorry Hot Tom!).
But flat circles aren't worth as much as the 109K's impressive climbrate and the near impossibility of overheating its engine.
Also, the 190D-9 is underrated in my opinion. It has the most balanced controls of all our fighters, and when flown with group tactics it is simply the best. Truckload of ammo, good visibility, fast, accelerates well, rolls like a top... the only place it doesn't shine is furballing on the deck, if that's anyone's thing.
Keep hoping for a Spit 14, P-47M, Tempest, or whatever...