Now this looks like fun! Seems like there's more Boxster/Cayman rally cars than I originally thought. Quite a few GT3 rally cup cars too.
But Topless has a point, do you really want to do this to YOUR car? If I had disposable income I definitely would but I'm that fortunate.
http://www.youtube.com/watch?v=D3U_NNnNAJ4
http://www.youtube.com/watch?v=T8vX6VHKvxM&feature=related
Here's the guy's car, interestingly the car weights 986 kgs.:
http://homepage.virgin.net/shalco.com/boxster_rally_car.htm