OK, I will go now ask if you did the maneuver of pressing down-up-up-down on the forward/reverse buttons on the steering wheel to put the StealthOne (S1) in Setup Mode (see page 7)after powering up the V1 and S1 and waiting about 10 seconds. If your S1 came from an identical vehicle (2006 e53) you may not need to do this, but if it was setup for another (say an e38) you do. This is where you first tell the S1 what car you have.
If I missed the post that you tried that already please forgive and ignore this reply.

PS If you found the correct iBus wire (on my car it is white, yellow and grey), it does not matter where you find one, so the mount you are trying to achieve should be routed to the nearest (most convenient for you) iBus wire.