Well I finally have caught up with the 21st century and got an iPod and installed the Dice adaptor in my Z4. The installation was straightforward, but (for me anyway) a bit more time consuming than some have said. By far the most difficult part was the removal (and reinstallation) of the carpet pieces.
The first piece to be removed was the carpet portion covering the trunk floor ahead of the battery compartment. This piece is held in with two plastic plugs (the kind with the barbs) and velcro and removed easily enough.
The next piece to be removed was the vertical piece covering the front (toward the front of the car that is) of the trunk. Poking through this piece of carpet is the manual top release, which consists of a small plastic disk attached to a string. I made two small slits in the carpet behind the disk and pushed the disk through the carpet (like a button through a button hole). When reassembled, the slits are behind the disk and not visible.
There are 4 plastic screws holding the carpet in place in the back corners. Removal of this piece involves using a flat blade screw driver to unscrew the screws while working your hands behind the carpet to hold the nut from turning. For me, this turned out to be the most time consuming aspect of the whole project. I found it very hard to work my hands behind the carpet while reaching deep into the trunk. The trunk is too small to “climb into” and I found the reach left me in an awkward and uncomfortable position. With a bit of persistence, I was able to remove the screws (without losing the plastic nuts behind the carpet) and fold the vertical carpet piece up and out of the way.
Photo of the right side of the carpet with the nuts removed:
Once this was done, I found a large box for the DSP unit (that’s what the label on it said anyway) mounted to the passenger compartment wall with a black metal bracket. The DSP unit was attached to the bracket with a Velcro strap and was easily removed. I started hunting for the CD changer connecters, but was not having much luck. I was tugging on a cable behind the bracket, but was afraid to pull too hard. I then removed the bracket (which was held on with 5 nuts of 2 different sizes). I was then able to see the cables with the connectors tucked underneath the plastic box which forms the back and sides of the center storage compartment. The back of this box is visible through the large rectangular cutout in the metal wall. I was able to pry up the bottom of the box with a screw driver and fish out the connectors. Next, it was a simple matter of plugging the Dice cable into the two connectors and plugging the other end of this cable into the Dice unit itself.
Photo of the bracket with the DSP box removed (note the connecters have already been installed in this photo):
Photo with the DSP re-installed (Note that the Dice unit itself is not visible, it will go in the space indicated):
At this time, I plugged the iPod cable into the Dice unit and tested the connection to the iPod itself. With everything working as expected I decided to begin reassembly. To route the iPod cable into the passenger compartment you could run the cable under the plastic box and through the punch out hole just below the hinges to compartment door in the passenger compartment. I decided that it would be to difficult to fish the rather large connectors on this cable in this tight space, so I drilled a ½” dia. hole in the back of the black plastic box and pushed the connecter from the passenger compartment into the trunk. I then reinstalled the metal bracket for the DSP unit and the DSP unit itself.
I then coiled up the extra wire (the cable is quite long) and tucked the unit up to the left of the DSP unit. Remembering what a difficult time I had removing the carpet, I decided to test the unit again before buttoning everything up. It was a good thing to, because I found that the iPod cable had become disconnected from the Dice unit. After reconnecting it, I used a tie wrap to strain relieve the cable and prevent the connector from pulling loose again (to do this I tightly wrapped a section of the iPod cable to the coil of wire running to the CD connectors leaving a bit of slack between the iPod cable and the Dice unit).
I then pulled down the vertical carpet peice and pushed the top release through the slit. Next came the most difficult part of the entire job, reinstalling the plastic screws and nuts holding the carpet in place. The good news is that the nut threads are designed with a one way taper which allows the screws to be simply pushed in (i.e.; you do not have to twist them together). It still found it extremely awkward to reach behind the carpet and hold the nuts, gather together the two carpet pieces, align the holes, and push the screws in place, all working blind, while reaching deep into the trunk. With this done, it was a simple matter to reinstall the carpet floor and complete the job.
So far, I have been thrilled with the sound quality coming from the iPod. The steering wheel controls work fine, and the song titles display on the stereo head unit, all as advertised.
The first piece to be removed was the carpet portion covering the trunk floor ahead of the battery compartment. This piece is held in with two plastic plugs (the kind with the barbs) and velcro and removed easily enough.
The next piece to be removed was the vertical piece covering the front (toward the front of the car that is) of the trunk. Poking through this piece of carpet is the manual top release, which consists of a small plastic disk attached to a string. I made two small slits in the carpet behind the disk and pushed the disk through the carpet (like a button through a button hole). When reassembled, the slits are behind the disk and not visible.
There are 4 plastic screws holding the carpet in place in the back corners. Removal of this piece involves using a flat blade screw driver to unscrew the screws while working your hands behind the carpet to hold the nut from turning. For me, this turned out to be the most time consuming aspect of the whole project. I found it very hard to work my hands behind the carpet while reaching deep into the trunk. The trunk is too small to “climb into” and I found the reach left me in an awkward and uncomfortable position. With a bit of persistence, I was able to remove the screws (without losing the plastic nuts behind the carpet) and fold the vertical carpet piece up and out of the way.
Photo of the right side of the carpet with the nuts removed:

Once this was done, I found a large box for the DSP unit (that’s what the label on it said anyway) mounted to the passenger compartment wall with a black metal bracket. The DSP unit was attached to the bracket with a Velcro strap and was easily removed. I started hunting for the CD changer connecters, but was not having much luck. I was tugging on a cable behind the bracket, but was afraid to pull too hard. I then removed the bracket (which was held on with 5 nuts of 2 different sizes). I was then able to see the cables with the connectors tucked underneath the plastic box which forms the back and sides of the center storage compartment. The back of this box is visible through the large rectangular cutout in the metal wall. I was able to pry up the bottom of the box with a screw driver and fish out the connectors. Next, it was a simple matter of plugging the Dice cable into the two connectors and plugging the other end of this cable into the Dice unit itself.
Photo of the bracket with the DSP box removed (note the connecters have already been installed in this photo):

Photo with the DSP re-installed (Note that the Dice unit itself is not visible, it will go in the space indicated):

At this time, I plugged the iPod cable into the Dice unit and tested the connection to the iPod itself. With everything working as expected I decided to begin reassembly. To route the iPod cable into the passenger compartment you could run the cable under the plastic box and through the punch out hole just below the hinges to compartment door in the passenger compartment. I decided that it would be to difficult to fish the rather large connectors on this cable in this tight space, so I drilled a ½” dia. hole in the back of the black plastic box and pushed the connecter from the passenger compartment into the trunk. I then reinstalled the metal bracket for the DSP unit and the DSP unit itself.
I then coiled up the extra wire (the cable is quite long) and tucked the unit up to the left of the DSP unit. Remembering what a difficult time I had removing the carpet, I decided to test the unit again before buttoning everything up. It was a good thing to, because I found that the iPod cable had become disconnected from the Dice unit. After reconnecting it, I used a tie wrap to strain relieve the cable and prevent the connector from pulling loose again (to do this I tightly wrapped a section of the iPod cable to the coil of wire running to the CD connectors leaving a bit of slack between the iPod cable and the Dice unit).
I then pulled down the vertical carpet peice and pushed the top release through the slit. Next came the most difficult part of the entire job, reinstalling the plastic screws and nuts holding the carpet in place. The good news is that the nut threads are designed with a one way taper which allows the screws to be simply pushed in (i.e.; you do not have to twist them together). It still found it extremely awkward to reach behind the carpet and hold the nuts, gather together the two carpet pieces, align the holes, and push the screws in place, all working blind, while reaching deep into the trunk. With this done, it was a simple matter to reinstall the carpet floor and complete the job.
So far, I have been thrilled with the sound quality coming from the iPod. The steering wheel controls work fine, and the song titles display on the stereo head unit, all as advertised.