M3 Stalls With No Warning (Hwy and Driveway)

I have a 1995 BMW M3 that runs like a top for a few days then "bam" complete loss of power/stalls unexpectedly. Leave for 5-10 minutes, fires back up and idles perfectly @ 500-550 RPM and can drive for a while and the problem comes back? Finally, after replacing Ignition Coils, Spark Plugs, New Air Filter (on K&N Cold Air Induction), Crankshaft Position Sensor, and not seeing this error state change, took to local BIMMER Mech., who says it has thrown the following code (desc): Control Unit Supply Voltage B+????
As a side note, the car runs like a top (placed a glass of H2O on the head and it just sits!!) and it runs like a scalded dog....that is until it stops running! :-)
Thank you in advance.

I recall that B+ was the feed to the alternator so that doesn't make great sense to me.
What does make a lot of sense is a failing DME relay or fuel pump relay. They are cheap and I would replace them both. What appears to be happening is the relay gets warm after use, fails and then stops. Sitting for a short period of time allow for cooling off and the whole deal is repeated. I suggest something like this or even an ignition switch failure because if it was somethng on the engine 30 minutes isn't enough time to allow the engine to cool down but something away from the engine like the fuse box where the relays sit or ignition switch area would sure be the right location.
Best suggestions I can come up with...

Possibly a fuel filter? Likely not, since you can drive spiritedly for a bit, but stranger things have happened.