I have a 2004 Z4 2.5. I bought the USSpec PA12BMW iPod adapter to use with my iPhone. I just got it installed today and it works well. There is a very helpful thread on this forum showing how to remove the center console in order to access the CD Change wires so that you can plug in the USSpec interface cable. I was surprised how much was involved in getting to this wire in the 04. It's behind the compartment for the center console, so you not only have to remove the center console, but you also have to remove the panels behind both seats in order to get the box out because (at least on mine) it has areas that go into the space behind those panels on either side. So, for anyone trying to do this, you need to look at the box in the compartment and see if yours has a recess area that goes back toward the speaker area. If so, be prepared to take off the rear panels on both sides behind the seats. All together the job took me just over 3 hours, but I took my time doing it.