Here is a DIY guide to retrofit S6 LEDs to a B7 (2005.5-2008) Audi A4 S-line or Audi S4. It would be the same process for other Audi A4 models, except that I’m not sure how much cutting would be required to make them fit. I have seen this done on a B6 before (2002-2005.5), [...]
DIY
Audi A4 B7 & B6 Escort Passport Hardwire DIY
Here is a step-by-step guide to hardwire an Escort Passport radar detector to your Audi A4. It should work for all model years but I know for a fact it will work for B6 and B7 models – and this will also work on just about any radar detectors, including Valentine One and Beltronics. This setup will make it so your charger cord is not visible, and the detector automatically turns on and off whenever the key is in the ignition and the car is turned on. This is great because it eliminates the need to turn the radar detector on and off yourself, as well as it looks a lot cleaner. It is also recommended that your radar detector is placed as high as possible, so this setup will give you maximum radar detecting capabilities too 
