The Dice DSP Adapter for BMW Vehicles is for interfacing the Dice BMW Integration Kit with the BMW DSP amplifier. Cars with DSP (stereo has an ampilifier with a mini coaxial cable attached to it) will not be able to use the Dice BMW Integration Kit without it.
 
To determine if the car has DSP, you must physically locate the amplifier and see it there is a mini coax cable and 3-pin connector attached to it. If there is a 3-pin and 6-pin connector available, then DSP most likely will not be needed. Please see the manuals section for DSP installation.