Vaccum leaks can do the same, in idle that is. My '82 Rover V8 has that attitude sometimes when it's hot and not a lot air gets to the engine (traffic jams and so). Needs some load to get revs down, ideally the engine get cooled down. Have to hunt the issue down.
Apparently it can happen with carbs in general. I knoe people tgat had issues switching this engine off in the desert because the fuel in the carbs evaporated and continued to be pulled in the engine. Which was hot enough to to ignite it for a while...