Damn, and I always thought it was so the Evo 8 could double as a salad shooter at high speed, just hit the gas and toss a head of lettuce on your roof!
Good paper link!
Another cool example of vortex generation is the intake on the Mazda Furai concept car. It had a spike sticking up off the roof which generated vortices and funneled them directly into the intake!
"The sharp element you see protruding from the roof is called an Air Fang, and was designed by the guys at Swift to optimize ram air induction. The air split by the Air Fang creates vortices which force air down into the intake. "