As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT 15,000 FT IN CRUISE, PILOT EXPERIENCED DROP IN ENGINE OIL PRESSURE AND DROP IN MANIFOLD PRESSURE. ON LANDING, FOUND ENGINE EXHAUST COATED WITH ENGINE OIL AND DRIPPING FROM TAIL PIPE. INSPECTION OF TURBOCHARGER INSTALLATION REVEALED LOWEST CHECK VALVE TO HAVE BROKEN DOOR FROM HINGE. IN FLIGHT LOOSE DOOR COVERED CHECK VALVE OIL OUTLET TO ENGINE OIL SUMP PUMP CAUSING TURBO CHARGER BEARING CAVITY TO OVERFLOW WITH OIL OUT ENGINE EXHAUST.