i'll check the PN of that unit in ETKA after work tomorrow, see exactly what it is. I believe the factory amp is tucked in behind the rear speaker on the pass side, but other than those 2 units and the harness that goes to the fuel pump, I can't think of any other wires running around back there

 

i took apart the rear driverside panel ( i got a suggestion from someone)
and still cant find it, but i did find some connections and a box with a bunch of plugs
im lost still and i really want to do this because otherwise i would have wasted all this time removing and taking apart my whole car. . .
pics:

 

4B0 907 357 is 'control unit for automatic headlight range control'

As far as I know, the unused harnesses in the back are for Nav.

Can't tell what the other one is, the one near the CD changer.

If you can give me part numbers, I can give you descriptions for most parts. I have access to the ETKA program you'd see the guy behind the counter using at the dealer.

Kinda tough to dig around for the part by diagram, there are HUNDREDS of diagrams.

 

ha, after posting that, i stumble across something.

That module with the 5 harnesses is the 'control module for central locking system'.

It doesn't say what the harnesses go to, but that module is a good starting place.

 

awesome thats gotta be it, now just to figure out which line is the antenna line. . p.s. where can i get some dealer software like that ? im looking to gather as much reference/ service software as i can for my audi

 

You can find them if you know where to look...hardest part if finding a working version

 

IIRC the transmitter is in the A-Pillar.

 

the box with the 4 plugs i took pics of is the locking/unlocking modual. i just need to find out which wire is for the antenna, there is atleast one thick black wire coming out but idk if its the right one and im not gonna pray and cut, unless i see more info.

i guess i gotta remove the rear plastics again and maybe the headliner. . .
interestingly i took out my antenna and it has a clear line coming of of it, and my fm reception hasnt changed since removing it. IDK im soo confused with this haha

 

antenna on the roof is for a car phone (you'll find a phone jack right under your cup holder). Radio antenna is integrated into the rear window.