Here is the FM Modulator I installed in my car. It connects directly in the car antenna (so we also need the converter kit). It worked out great; the device filters out the unwanted signal coming thru the car antenna. It all fit behind the dash under the stereo.

http://www.installer-data.com/item/d...php?it=FMM-100
http://www.installer.com/item/displa...php?it=40-sb30
http://www.installer-data.com/item/d...hp?it=IPOD-RCA

VW / Audi / Mercedes Radio Removal Tools
http://www.installer.com/tools/#