I've been following this thread from the very beginning, and I must say that I didn't have the slightest idea of what could be wrong.
One thing however disturbed me - the fact that the stalling issue wasn't there from the very beginning. Now, after reading the response from 998S, I recall that I had idle problems on my bike every once in a while, without stalling though.
I further recall that I knew a guy who was with BMW engine development (cars) and who was very excited about getting my used fuel filters for lab purposes. I also dug out from the depth my brain cells that I've emptied my bike's fuel tank once and was stunned about the contents, which I also presented the engine guy.
LJH, if not already done so, try to empty the fuel tank, spill-clean it and replace the fuel filter if there is one. If there is no filter, check out if you could install one (not so easy if the fuel system wasn't designed for a filter in the feed line).

Just another idea.