If you let a Spit or La7 get 400 yards off your 6, you are basically dead.
You could resort to the JB evasive, which is flopping around while headed to the closest ack (even if it is 50 miles away), but that won't work real well against a plane with Hizookas, or a plane with more than 1 normal 20mm.
If you have a little bit of alt, dive. They'll think you are trying to run, so chop throttle and cross your controls (full rudder one way, ailerons the other to keep the plane 'straight', you'll fly crooked), roll, or something to bleed off speed. Once you get them right off your 6, firewall the throttle and run.
Doesn't work so well if you get caught slow on the deck though.
Even then unless they are marginally faster and close you have some options.. it is relatively easy to force and overshoot and bleed their speed down to where you can safely run away if they start much faster than you, it is near impossible to do it if they are only a little faster to begin with.