The Best I've had so far with my GT, Ford GT BTW. Anyhow, I've been able to get 1346 max on... i think 1/4 mile. Um... here's what I did.
Maxed out my car with Level 4.
(I'd like to rephrase the above sentence, your car does not need the all mighty level 4 parts. You could do this with level 3's and 2's. Maybe 2's not sure but still, give this a try and I swear it'll work.)
Suspension: all were moved to the left (compression, rebound, spring rate, ride height) and these were moved all to the right (Front and Rear Tire Pressure
Engine: Start and End Boost moved all to the right
Drivetrain: all were moved to the left except Final Drive Gear (after moving all the way to the left, moved 4 clicks right)
Brakes: NUthin
Enjoy.