Doubt all you want, I went through exactly this behavior with a manifold vacuum leak on a BMW. When the engine is cold, it runs open loop (rich). When it warms up, the ECU tries to control fuel trims. The EHA has a limited degree that it can control the fueling to override the MAF plate on the fuel distributor, if there's enough of a vacuum leak, that can be enough to make the engine run lean enough when coasting or braking to stall. Cold air (especially if damp) makes the problem worse since it is denser than hot, dry air.