OM642 Vacuum Pump Failure / Oil Feed Issue

Has anyone encountered such a problem with this engine in any of the 320 CDI cars? Could it be caused by carbon build up even although there are no other symptoms whatsoever of such a problem? The engine is serviced with oil changes and I checked the filter which looked perfectly fine. Is there any way of fixing this without removing the cylinder head to check the oil feed?
Have anyone converted to an electric vacuum pump like a Hella UP28 Power Brake Booster Vacuum Pump or similar?
Any experience appreciated.



