I've noticed this too.
-Pave any gravel driveways that you may encounter
-Dont drive the car in the rain
-Garage the car
-Wash it daily
Follow these 4 easy steps and you'll never worry about it again!
Alot of it is caused by the very rich tune our cars have from the factory. When you mash the throttle on this guys and hit boost, we look like mini diesel trucks with all the black crap that blows out of the pipe. i dont even think a rear diffuser would work.