Until the other day I would look at cable first but I had the hose drop off the boost gauge resulting in pressure drop in manifold which should have resulted in much smoke from rear and increase in temp as the air fuel ratio was way out of whack, but what happened was the van lost power and the gear box went all strange with clunky shifts etc. My first thought was fuel filter and service the gearbox, but what had happened was the clever little chip had sensed the lack of air and cut back the fuel and what it did to the gearbox I don't know. I found the hose off replaced it with a new one and all is well again.Moral of the story is it ain't always the obvious, though I hope it is a simple fix for you like galo55's.