I am new to this forum and wanted to try to obtain some information about the existing stereo wiring in my new 2002 TT. I am upgrading the stereo system to an Alpine DVA-7996 non-powered (CD/DVD) head unit with the ancillary navigation unit (NVE-N852A). This will allow CD playback, DVD viewing and navigation. I was told that since the BOSE factory system already incorporates amplifiers I simply needed to get Soundgate's ISO4 noise isolator to make the Alpine's 4 volt pre-outs compatible with the factory Bose's amp. I did not want to upgrade the amp or speakers at this time. After painstakingly connecting this in accordance with Soundgate's direction, I do not have any sound. Does anyone know anything about the factory sound wiring and how I can solve this dilemma? Also, I found the factory amp in the spare tire compartment. Is this the only one?