ukrcan,
For what its worth, the GROM worked perfectly on my '08 MCoupe without the DSP adapter. That car have DSP, but it also have both the 3 & 6 pin connectors (I believed the E85/E86 Z4 have similar audio systems to our E53 X5 & E83 X3).

I love the unit thus far. My only complain is the MP3 tag display on the NAV screen is horrible - only displaying 10 characters. I'm trying to get them (GROM) to see if they can display the MP3 tags on the full screen, similar to what the OE CD player would if you were to play an MP3 disc.