I have this Alpine unit XM interface from my old car and wnated to hook it up in my 04 A4. I don't have Bose. Is the shark fin one or two antenna leads?

I am installing a pioneer unit now that appears to fit, I'll fire it up and let you know how it works.

Just finished the install of a pioneer aftermarket system with fm modulator. The xm antenna works, but I had to switcht the antenna connectors (the green cable went to the brown connector, and the brown to green) -- so much for standardization! But otherwise it works great!

I will post pics next week; you need to pry the cover off that is under the compartment panel in the trunk on the left. It needs to come straight out or you can break it.

then, fish around behind the panel and you will find a harness with several wires and two for the xm/sirius. You can take the power and ground from that harness, and you may be able to get switched power as well. You may need to remove the entire trunk liner on that side to find the harness -- it is loose back there and has a tendency to get lost. Email me with any specific questions.