As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE ENGINE SURGED 4-6 LBS OF TORQUE WHEN THE POWER LEVER WAS RETARDED FROM 45 TO 30 LBS OF TORQUE. THE TORQUE WOULD STABILIZE WITHOUT POWER LEVER INPUT. THE PROBLEM ONLY OCCURRED DURING DECELERATION. A NEW FUEL CONTROL UNIT WAS INSTALLED AND THERE WAS NO FURTHER PROBLEM.