As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE WOULD RUN ROUGH AT ALL POWER SETTINGS. AFTER INSPECTION FOUND THE NR 3 CYLINDER ON THE RT ENGINE CRACKED FROM THE TOP SPARK PLUG HOLE EXTENDING AROUND TO THE BOTTOM SPARK PLUG HOLE. CRACK IS VISIBLE FROM EXTERIOR AND INTERIOR OF CYLINDER ASSY.