most are for looks... the STI and EVO are a rare exception (along with the likes of Porsche and Ferrari).

I don't know what the AP1 or AP2 wings look like...

 

sorry, i forgot to respond to this earlier.

I can tell by the relative angle of the wing to the trunk, and I can also tell by the curvature of the main element, and then comparing that to your avatar pic.

Here's an easy way to tell:

spray a mist of oil over your wing before you go out on track. It will leave thin streamlines showing you what the air is doing. If there are straight, uniform streamlines right to the trailing edge of the wing, then I stand corrected; however, if the lines break up and go all spotty and random, then the flow is separating from the wing and you are running too much angle.

give it a shot and see what happens.

 

Most of these "wings" are not wings at all, but spoilers. Wings work by accelarting air to create low pressure on one side, creating downforce. A spoiler disrupts the flow air, generally in an attempt to reduce drag and also sometimes to decrease lift. A spoiler on a car that is not creating lift will not add an appreciable down force.

I have not done any analysis on the S2000 and its spoilers, so I can't say if they actually do something or are just cosmetic. The Evo and STI seem to be exceptions to the rule and offer real wings. However, I believe these wings are fixed,and being able to adjust your aerodynamics to specific track speeds makes them much more functional.

 

Thanks!