[Tom Goldman]

Cleaning up the air in front of the car almost always helps , but a lot of times the increase in speed is caused by the change in overhang in front of the wheels picking up the trap lights differently.
It can also play hell with driving the stripe if its above the beams until you drop the nose.
You drop the car and it goes quicker !
Ask any Stocker with a 4th gen Camaro about that one.