[docurley]

This may help

On the S4 model, there is a small-upholstered box that is wedged in the corner closest to the passenger-side brake lights; remove that box by pulling it vertically, and put aside. Next, pull back the sound proof carpeting housing that is on the inside of the trunk lid on the passenger side. It is secured by two standard auto clips see picture below (circled in red).

Once you have removed the two clips, pull back the soundproof carpeting and you'll see the tail light assembly. There are three plastic clips holding it in place. First loosen the clip closest to the outside of the car, then the top one, then angle the whole assembly towards the front of the car. (see picture below):
Before After