There might be other boost leaks, not just that one. Check for burst hoses too, particularly if your car's a few years old.
They're easy to spot if the engine bay is clean (don't pressure-wash the engine bay though!). Look for black oily emissions, the diesels always have dark oily vapours in the air stream after the turbocharger because of the PCV (small hose that connects just in front of the turbocharger). The oil is supposed to be there (because it gets combusted), but it handily also shows us where boost leaks occur.