That Voltex wing is hot! At speeds over 150kph they would definitely generate some downforce. But they are all adjustable, it would be import to get the angle of attack right, its a balancing act, if the angle is too great the air separates from the underside and they stop generating downforce, therefore drag is reduced, just before that angle, downforce is at its greatest, but so is drag. This is the principle behind the 'F-duct' used on several MY10 F1 cars. It is definitely a science.

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F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i