Your BMW dealer doesn't want you to know this....
Post '84 dual outlet Bosche coils will all eventually crack and fail. They're expensive to replace. Really expensive.
Stock HD/Buell dual output coils can be found on e-bay for about $1.oo. They're take offs from folks who've bought into the HD "dual fire ignition" myth. Good on them, I say.
I've had one on my '92 GS/PD for 30k kms now without issue....