What was found
(CAN) ENGINE STARTED RUNNING ROUGH AND LOSING POWER, SO AIRCRAFT LANDED. POST-FLIGHT INSPECTION FOUND THE NR 2 CYLINDER EXHAUST VALVE BROKEN AT THE STEM. COMPRESSION CHECK OF ALL CYLINDERS WAS LOW. ALL CYLINDERS WERE REMOVED. NR 1, NR 3, AND NR 4 CYLINDERS WERE CRACKED. METAL WAS FOUND IN THE OIL FILTER. THE ENGINE WAS REMOVED AND WILL BE EITHER REPAIRED OR REPLACED.