As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED ROUGH RUNNING ENGINE AND LOW RPM. MAINTENANCE FOUND NR 4 CYLINDER HAD EXHAUST VALVE STUCK OPEN, NR 4 CYLINDER PUSH ROD AND HOUSING WERE BENT WITH NO OIL LEAKAGE. THE PISTON WAS NOT DAMAGED AND NO METAL FOUND IN THE ENGINE OIL FILTER. (X)