As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED A ROUGH ENGINE; "MISSING" WHEN PROPS BROUGHT BACK FOR CRUISE AND STRONG VIBRATIONS ON FINAL APPROACH. MAINTENANCE INSPECTED AND FOUND THE LEFT ENGINE NR 4 CYLINDER EXHAUST VALVE GUIDE TO HAVE PLAY, THE EXHAUST VALVE CHIPPED, AND THE EXHAUST VALVE LIFTER FAILED. THE CYLINDER WAS REPLACED WITH NO FURTHER DEFECTS NOTED.