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Martin, it looks like you're doing a great job of cleaning things up.
I have Webers, not Dellortos, but they're alike in many ways. One thing I noticed is that your carbs were dirty on the outside, from the tops on down (before cleaning). That's often caused by leaking needle valves. After shutdown, pressure in the fuel lines causes the bowls to fill and overflow out of air passages at the top of the carbs, letting fuel seep down the outsides of the carb bodies. Another symptom of that is a heavy odor of raw gas starting a few minutes after shutdown. The rebuild kit should solve that.
Also, I've been remarkably lucky avoiding the typical 'dirty idle jet' symptoms that are so common with these carbs. I think the main reason is trying to not let the car sit for more than two weeks without running it, for at least a short while. Granted, this is a lot easier in a mild climate, but there's really no better solution to chronic carb problems than just running some fresh fuel through them as often as possible.
Good luck!
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