As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED THE LEFT ENGINE RUNNING ROUGH, AND CHT SHOWING 175 ON LEFT ENGINE. MAINTENANCE INSPECTED AND FOUND THE LEFT ENGINE CYLINDER NR 3 EXHAUST VALVE BURNT AND THE NR 4 CYLINDER EXHAUST VALVE BROKEN; BOTH CYLINDERS HAS A TOTAL TIME IN SERVICE OF 1382.2. BOTH CYLINDERS WERE REPLACED WITH NO FURTHER ISSUES.