how about them spoilers?
#15
Actually spoilers are supposed to push the rear of the vehicle down to improve it's contact with the pavement at high speeds. Since the aerodynamics tend to lift the lift the rear of the vehicle the spoiler goes there. Race cars also employ an air dam in the front to accomplish the same up front.
#16
AKA, downforce & traction.....
Yes, the air dam is to keep as little airflow from going under the vehicle as possible, but to move it around the sides.
#18