If your looking for function you should give up right now. There isn't much function that can be had. Giant wings may work for downforce on a RWD car, but when we're driving FWD cars that can't go fast enough to NEED downforce.. well it's useless.
And the cooling abilities of aftermarket vents/ducts are pretty minimal for a stock ride. Unless you had something routed to the intake I can't see it being very useful.
If you're going to put that kind of stuff on the car, at least do it for looks. :thumbs up
Just don't cheap out on the fiberglass vented fenders and stuff, because that stuff will crack very easily and look horrendous.