That is excellent Kweassa.
P-38 has many severe weaknesses vs most of the planeset.
1)It compresses badly, so if you in a plane that handles past 420 mph, go for a dive and get away.
2)Believe it or not, its a hard plane to "lose E" on "purpose". Most planes being sciscored by a 38 just have to hard rudder and cut engine and bingo! 38 is on their 12 oc with low E and as you all like it : with the planform facing you. Do this only if your plane has an accel similar or better than the 38. Otherwise the 38 will extend flaps and turn you over.
3)P38 will not retain E past 400mph below 20k. So if you see a 38 dive away to escape, keep your alt or do a shallow dive to keep up at least 400mph. The 38 will blow its alt to get to 490 mph... will stay at that speed for about 10 seconds and then, if below 20k, it will slow down to 340'ish a few seconds after that (maybe a bit more if 38 still has WEP, but it will slow to below 400 guaranteed). You will notice that because you will sudenly begin to gain on it quickly.
4) 38's blind spots are low 7oc, low 5 oc (tails block view), low 9oc and low 3 oc (big wings). Ive seen many planes try to sneak up on me from below 6 not realizing ive been seeing them for miles away.
5)Low rate of roll at slow speeds (below 380ish mph). This only helps you if the 38 is real close to you, you can flip flop the 38 into losing you. However, the 38 CAN match and stay on your 6 by using rudder to help it roll (it can roll as fast a jug like that) a couple of times. And many pilots out there just cut engine and let the flipfloping plane lose its E and dance left to right on its gunsight while he sprays and watches the fighter fly into his bullets. In short, do it only when the 38 is at d300 or closer.
6)38 has a good accel from 0 to 200mph. Dont get into a slowfight with it unless you have a good accel or a turnfighter like zeke or spit. You said you fly p-51 and tiffie, the ONLY times ive been able to shoot them down when 1-1 is when the tiffie or pony try to do turn with me or stay in close proximity (aka co-e within d2.0). 38 will out-accel the p51 and will out-turn/climb the tiffie. Do one pass on the 38, extend to d5.0, climb and turn then come back and repeat. If you dont the 38 will cut inside your turn and spray you.
7)38 has very poor y-axis control when above 350mph. Many 109's and spits and p-51 usually dive to speed, and, if they run out of alt to dive to gain more speed, they pull up hard on me and split-S on the top of their climb before ive even gotten my nose above the horizon. Makes a very annoying situation for the P-38.
8) finally, its a plane made of glass. Take any shot no matter how far fetched it is. 1 ping will cripple it almost guaranteed. You can be assured you will either kill 1 engine or blow an elevator (at which point the 38 is SCREWED because it will nose up or roll about 40% of what it would normally roll/nose up. And thats BAD) or rip off the tails.