And those are what!?! Would the dealer install those if I opted for the Aero package... He said he can put the spoiler on, but I forgot the Aero package comes with that, so does anyone know?

 

They consist of 4 plastic pieces that are designed to be bolted underneath your rear bumper / fenders (on either side of the exhaust) and what they do is "smooth out" or in actuality cover up the gaps / pockets torward the rear of the car (where air can be trapt). This in return provides for a better and smoother under carraige air flow, which is essential when you have a wing on the trunk, which is causing more down force on the rear of the vehice. The defusers help balance everything it out.

So the next time you see "those guys" with the HUGE formula like wings on their cars, check to see if they have anything underneath their car to help balance the forces out. Chances are they dont, so in essense that HUGE wing is doing nothing but slowing down that car, and its not solely from the down force, but rather the air turbulance underneat the car (air being trapt underneath, and then amplified by the wing) - an area often forgotten about and very rarely touched on...

Hope this helps . . .