Hi,
the video gives you a step by step tutorial how to replace the steering gear boot at your Audi C4. This is a rather difficult repair because the steering gear has to be removed for replacing the boot and this is not very easy.
http://www.youtube.com/watch?v=h8qQ1KiV818
The video has a German soundtrack, but English subtitles are available at YouTube. If you don't see them by default, watch the video directly at YouTube and press the setup button beow the frame.
Enjoy it,
Jürgen