You can see pics of the OEM rear valences on Glenn's car.
http://www.stillensucks.com/
I think its clean, but I dont like how it doesnt like up "perfectly" with the sides... I opted for fpr copies of the factory valences, except that the angle where it meets the sides is more "aggressive" and lines up better with the side skirts.
The factory rears are a little
too clean for my tastes.