Sorry to hear that your still having hunting issues.
Do you still have the BMW diagnostic connector in your engine loom? If so you can get a code reader from a company called Peake.
http://www.peakeresearch.com/
They do come up on ebay from time to time but check the Peake website to make sure you get the right version. You can read codes and reset them to fault find. Very useful!
I had a hunting problem on my M52B28 (MS41 DME) but only in the 400 to 600rpm range and a cycle time of 2-3 seconds. It only happened after I changed the DME to a EWS deleted version. It turned out to be the engine temperature sender. I'd try checking the temp sender wiring connector first as it may be intermiitant and causing the DME to think the engine is cold. Incidentally, I had it confirmed that the MS41 DME adaptations are not lost when de-powered.
Good luck, Peter