Hopefully someone who is familiar with car audio can help me with this annoying problem. I have a totally stock stereo in a 2003 Passat and it works great. I purchased and installed from VW a Phatbox MP3 player that connects to the factory installed CD changer connector in the trunk. Phatbox works as advertised except I get a high pitched squeal/hum/whine that is very noticeable. The noise does not seem to change with changes in engine RPM or (heat, a/c) fan speed. I hear no hum when listening to a single CD in the head unit. I only get the hum when using the Phatbox. Could the Phatbox itself be faulty? Or possibly the factory installed CD changer wiring has some sort of issue?