It is motor racing tradition that a car that won either Le Mans or anyother important race not be washed afterwerd, its almost like battle scars from the event.
http://en.wikipedia.org/wiki/Balsa
Starting with the Bergspyder cars of the mid to late 60's when Porsche began studying every form of light weight material to use in their race cars, they began to use balsa wood in the shift knobs.
That's why the Carrera GT knob is balsa wood instead of tacky carbon fiber.
It's tradition, something Porsche knows a little about.
http://www.seriouswheels.com/pics-pq...or-Console.jpg