Visit www.v12uberalles.com for an interesting article on rebuilding the wiring harness for the throttle actuator on a v12 motor. The M120 (if I've got my model #'s right) V12 motor is just 2 M104's "joined" together, so there may be some similarities.

The guy that created that site is a real detail-oriented individual determined to fix things the right way, and fix them only once.

Maybe there will be something you can glean from his space.