Aerodynamics have really changed modern racing.  Most high speed cars use a large wing like this McLaren above to make the body of the car push down harder on the tires.  This effectively increases the normal force on the tire to increases the frictional force of the tires. (Physics of Racing)  Of course this large wing creates drag, so most wings have a low angle of attack. (Auto Math)  Some Formual 3000, F1, Indy, and GTP cars use large scoops on the side that are shaped like an hour glass, with a small hole under the body. This creates a low pressure system under the car and sucks the car to the road.  There is an old racing storie that before Indy street races workers have to go around and spot weld the man hole covers so they are not sucked off the ground during the race.  The louvers on the McLaren help control this low pressure system under the car, and cool the engine.