Certainly sounds a boost hose issue to me,they're the same engine as a Volvo I believe and i've just removed a turbo on one this week.from the airbox into the turbo inlet pipe via a big connector where there's loads of little pipes which are boost related,anyone of them could be split with ease,especially as some of them are really awkward to get at and some heavy handed apprentice may have pulled rather than undone a pipe causing even a loose connection,try down there young man.