hey there. ya this seems to be common (at least for me it is). I tow a 9k lb enclosed race car trailer and after a 500-1000 mile tow the truck will run it's absolute best the next week when driving unloaded. back when i was using a combination street/track car for 'fun' events and was driving it to the track and not towing it to the track (both my current racecars are true full on racecars without interiors running full cages and no insurance or registration or plates so I always have to tow them now!) -- the week after a two day track event (where I'd put 4 hrs or so full throttle track time on the car/engine) it would run INCREDIBLY well driving back and forth to work; mpg would be up 3-4 and the motor and car would just feel more powerful and smooth.
I always just figured that the injectors were super clean and the combustion chamber was cleaned up and the motor was so called 'blown out with a Italian tuneup'. so ya, when you work them really hard they seem to run better the next several weeks or so.
