I agree with CWMV. What is also annoy me the fact that the P-47 is much better in fly than the P-51D in this game... 
It's hard to make something out of nothing in the '47 though. She runs out of tricks pretty fast if you don't have the advantage and then she flounders around like a whale in a wading pool once you run out.
It can be done but not by many people, only a special few

The P-51, on the other hand, doesn't have the same response from it's engine in terms of torque or horsepower but it does have two other advantages which rely upon your ability to
keep the slip ball centered. In the P-51 you get the advantage of a better thrust to weight ratio as well as a much cleaner aerodynamic profile but neither of these mean jack-shit
unless you're flying trimmed and coordinated. If you're out of trim the P-51 is about as aerodynamic as a furniture van, just look at the cross section of the fuselage.
Make the most of the aerodynamics of it by flying cleaner than you do in other aircraft.
What all this boils down to is that, so far as single-player Il-2 goes, CWMV is right. The P-51 sucks a big floppy donkey dingus.
Not because it's a bad plane but because the AI cheat.
You are flying it against IDEAL versions of aircraft that were plagued by various technical problems and other shortcomings in real life.
Your opponents don't have crap fuel, poorly manufactured engines or faulty, over-complicated and often sabotaged weapons systems. (Slave labour is bad m'kay)
Your opponents are not sane, rational people who fly like they don't want to be killed, they are fanatical, super-nazi-banzai cyborgs and you can't win against the cyborg flown 109 or 190 in a pitched battle with the P-51. You're John Connors in that Terminator world and, anything like the kind of fight that we all usually want to have in Il-2 is taboo in the P-51 against the AI.
(I mean a quick, fun fight and not a long, boring game of cat and mouse.)
So, for the offliner, the golden rule of P-51 is:
"One pass, haul ass."
Use guerrilla tactics, cyborg bitches don't know 'bout my Che Guevara handbook.
If you deny the enemy the chance to be effective (say by driving him away from your bombers and forcing him to sacrifice height to escape) then you've done your job until he comes back. Don't chase him, let him sniff around and try again and, when he does, have another go at him. Only get stuck in when you hold all the cards, if you don't hold all the cards then fold, you can't bluff a cyborg.