Def for the Fogs as long as you dont have the S4 I believe then the grilles for the fog lights come out and you can reach your hand in there.

 

I can't find the site right now, but there was an installation guide for an HID conversion for the A4 lights and it showed that you need to cut into the headlight to put the cable from the ballast through or something like that. Do you really need to cut holes in the headlight?

 

You drill hole in the back of the plastic cap behind head light to make bigger holes for the bulb. Then they will give you some weather proof double sided rubber seal thing that will make it so nothing gets in pretty easy you will figure it out.