The thing about stuff like that is you don't know its working just cause its there, the aerodynamics of the car could just be carrying the air above them, there for eliminating there potential. Real world testing would be good, get a thermometer and mount it in the engine bay some how, cover the vents and take a drive. Check the temp. Wait a little bit for the engine bay to cool, then uncover and drive. Remeasure the temp. Duplicate the same drive and style. Its a very week test but if it does show a difference then you can get some cred instead of looking like a ricer.