As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE, AIRCRAFT EXPERIENCED VIBRATION. CHECKED COMPRESSION ON RT ENGINE, FOUND NR 3 CYLINDER HAD 0/80. REMOVED CYLINDER AND FOUND CRACKED FROM SPARK PLUG HOLE TO INTAKE SEAT. INSTALLED NEW CYLINDER AND GROUND RAN. ACFT WAS RETURNED TO SERVICE NO FURTHER ISSUES. NO INDICATION AS TO THE CAUSE OR RECOMMENDATIONS AS TO HOW TO PREVENT REOCCURRANCE.