Have you carried out a plug check after one of the stalling episodes?
My suspicion is that this is a carburettor problem rather than an ignition problem. Having said that, I once had an curious problem on a Crossflow engine which would not idle below 1200 rpm - it turned out to be the bob weights in the Motorcraft distributor having seized.
Have you checked the accelerator pump diaphragm? If its perished it should drip a little petrol when you operate the the throttle lever and if it let's petrol out it will probably let air in. A new one is included in a genuine Weber service kit.
Arwyn
