original '70 one-carb Mini, not a Spridget) has a problem with the engine
dying whenever I take my foot off the accelerator.  It idles fine, runs fine
without loss of power at speed in all 4 gears, and doesn't miss, either
while idling or at speed.
Would a leak in the distributor vacuum advance exploit this if the manifold 
vacuum changed quickly, ie. you rev it and drop the idle fast?  Can you 
check ignition timing with a light easily in a mini?  Try it at several 
throttle transient times, since it does sound like you can make it run if 
you drop the revs slowly enough.
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