OK, I'm not an aero engineer but I did play one on a regional level for 5 years on a FC team. The racer's bible on the subject is Joseph Katz' Race Car Aerodynamics : Designing for Speed. What I have read and discovered through much testing is that you can create a tremendous amount of down force with little or in some cases (the diffuser) practically no drag if designed and setup properly.

Down force, as its name implies, increases downward loading on the tires w/o increasing the cars weight at high speeds. This additional load allows more side forces to be created at lesser side slip thereby reducing the heat and subsequent wear due to frictional force. Plain and simple the car sticks better in the turns even with a smaller contact patch. Also, aero can be used to effect weight transfer during high speed braking as the aero loading can be larger than any weight transfer that is occurring. While inducing some drag at its location aero elements can and do reduce overall drag of the car at speed.

Some may have noticed the common factor is high speed. Most aerodynamic elements and especially wings require a decent amount of speed to be effective. High speed corners like 12 and 1 at Road Atlanta are good examples for those familiar with the track. The slower the speed the larger the element must become to be of any use and then you compromise any down force gained with added drag. Unless you want something the size of Texas hanging off your car think about where you race and if aero would get you anything. At some tracks we would flatten or remove elements due to the speeds involved vs. any drag that may be produced.

The vast majority of the crap I see hanging on cars of the tuner, ricer or whatever category you want to call them are all drag and little or no down force. Even if you had access to a wind tunnel for testing I would suspect the amount of down force generated as a percentage of overall weight of the car would be pretty dismal not to mention the drag induced. These "sculptured" elements are more for looks than record books and as my esteemed colleague Mr. Amy expressed they look gay.

Many aero elements can and have been fabricated for fairly cheap when compared to other go fast items. Properly designed they can be easily adjusted at the track so you can get real data to back up any ideas you want to try. Do they have a place in IT? I haven’t given it much thought as I'm more interested in getting things like jacking plates added or removing vestigial street car items in order to make my racing easier and cheaper.