As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN FLIGHT, THE LEFT ENGINE N1 AND N2 FLUCTUATED. THE LEFT ENGING WAS JUST BROUGHT DOWN TO IDLE AND STILL PRODUCING THRUST. AN EMERGENCY WAS DECLARED. LANDED SAFETLY AND WAS ABLE TO TAXI TO A GATE UNDER ITS OWN POWER. MAINTENANCE REPLACED THE LEFT GEAR BOSS ON THE ENGINE.