As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SUBJECT AIRCRAFT IS LOCATED IN AUSTRALIA. IT WAS REPORTED THAT THIS ENGINE WAS SURGING IN-FLIGHT. INVESTIGATION THERE FOUND A TURBOCHARGER WITH 'EXCESSIVE END FLOAT'. THE TURBOCHARGER WAS RETURNED TO ALLIED SIGNAL AND INSPECTION FOUND A WORN THRUST BEARING.