Call me finical, but I'm not very inclined to give help & tips in this forum to players tossing around childish insults in their questions. But that's just me and others may disagree.
It's just not the way I want to see this community developing.
EDIT: I see The original message was edited to some extend... Much appreciated

Now on topic: If you have to climb to their altitude to catch them and they decide not to engage you, you are usually out of luck.
Show 'em your tail, lure them back down. Or disengage, get out of icon range and climb climb climb. Chances are good they come back looking for more cheap picks (I usually do

).
Best planes to hunt down P-51's are Tempest, La-7 (below 10k) and to some extend 109K-4, Spit XIV and 190D.