One of the problems with racing front drivers is getting the rear tires up to temperature for proper traction.
I would imagine any rear down-force that can be had is good for handling. There is usually a very low spoiler in the front for front down-force.
I remember watching a euro-racing thing of "Street Stock" VW TDi's and when they would corner hard, they were set up to lift the inside rear tire. That's what they had to do to corner fast without a big wing on the trunk lid.
Well my Jetta TDI is set up with the same body as the TDI CUP race cars, the front end is not offered as an option and must be dealer or user installed, it does have a completely different shape than the stock front end. I also have the silly little wing on the trunk. Honestly as Al wrote, "for looks" because it does not seem big enough to provide any real downforce but its the same wing as on the TDI CUP racers.
Below is a picture of the TDI Cup front end (aka "Thunderbunny" front end) on my TDI Jetta. I'm not sure that there is any additional downforce provided by this front end, but it clearly offers more ability to suck air into the engine area.
Here is the standard front end of the TDI Jetta, there is less grill area and the shape is more rounded.
Here is a photo of some TDI CUP racers, you can very clearly see how small the tail wing is on these cars. I'm still not sure that the wing can offer any real downforce?
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On the same theme. Do you remember the Buicks from the 50's and how they had the small oval shaped vents on the front fenders in front of the doors? They sell fake Buick fender vents and I see many blacks and Mexicans putting them on everything, Nissans, Pontiacs, Hyundias!
I saw them on a pimped out HUMMER the other day!