As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED ENGINE RUNNING ROUGH. MX FOUND NR 4 CYLINDER EXHAUST VALVE HEAD BROKEN OFF AND MISSING. THE CYLINDER HEAD AND PISTON SURFACE WERE SEVERLY GOUGED. THE TURBOCHARGER PN 409170-9001 ALSO HAD SEVERAL BROKEN AND DAMAGED TURBINE BLADES. NR4 CYLINDER ASSY AND TURBOCHARGER REPLACED ENGINE OPERATION CHECKED SERVICEABLE.