I've not been able to find any handling notes for the P-38, though you will do ok if you just keep the airspeed up in combat, and don't get suckered into a turning fight.
You might find the pilots' manual for the real thing of interest: download here -
http://aafcollection.info/items/deta...1!title!up!100. Though the sim doesn't model everything, you'll maybe get a few clues about how to make the best of the P-38, and maybe appreciate it a bit more too.