Regarding stalling issues brought on due to riding in rain, I may have a solution.
My f800 has done this and the last time it stalled in the rain I was near my dealer and brought it in. They opened the air box to find standing water ( about 6oz or so) in the air box. The idler air by pass valve is located on the bottom of the air box also.
When you close the throttle to shift or come to a stop, the air idle by-pass valve opens and sucks in the standing water stalling the motor.
My service manager concluded that the air intakes are letting in a significant amount of water during heavy rains. (ram air effect)
My service manager and I came up with a way to block rain from getting into the intake with out restricting air flow.
I have tested these block-off plates in a very heavy rain yesterday and I could not get my bike to stall after 25-30 miles of interstate riding.
I experienced stalling a dozen times before under the same severe rain conditions with out the block off plates.
Let me say that I tried to make my bike stall the other day in the rain under every throttle position and rpm/gear/load condition and it ran perfectly.
The plates do not effect performance that I can tell during normal weather.
The service manager and I both ran the bike up to 100mph and could not tell anything different from a stock bike.
BTW Gateway BMW is my dealer and they have been very good to me
Hope this may help!