my brother has the same van and the same trouble it went back to the dealer a few times ive looked at it several times and could not fault it even fitted a new egr which made no difference in the end my brother i think has sussed it out it seems to be the dpf regenerating he says that bang on every 400 miles on a longish it will start smoking the engine gets very hot he lets it tick over when he stops and when he restarts its fine then 400 miles it does it again ?