As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) RT ENGINE DEVELOPED 'MISSING OR SURGING' IN POWER AT HIGH POWER SETTINGS. RAN FINE AT LOW POWER. AIRCRAFT RETURNED FOR MAINTENANCE. AMO REMOVED MAGNETO AND FOUND DISTRIBUTOR BLOCK CRACKED AND BEARINGROUGH. MAGNETO REPLACED AND GROUND RUN, SERVICEABLE. MAGNETO PN 10-682912-18, SN H259310.