As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENG NR 1 STARTED BACKFIRING NUMEROUS TIMES WHILE IN CRUISE FLIGHT, AFTER 1 VIOLENT BACKFIRE, THE ENGINE WAS SHUTDOWN AS A PRECAUTION SO AS TO NOT DAMAGE THE ENGINE EVEN MORE. A NORMAL LANDING WAS PERFORMED. NO DAMAGE AND NO INJURIES AND THE MAGNETO WAS REPLACED AND ENGINE GROUND RUN SERVICEABLE.