I believe the Plus 8 uses can bus wiring, in which case the wiring of extra lights might not be straight forward.
AFAIK John is correct.
Also, the Canbus software isn't BMW but rather a base system that has been modified by an engineer specifically for MMC. This is where some of the minor glitches with S4 Aeros stemmed from and therefore I spent some time speaking with the factory to understand what changes they had made to remedy them.
