What was found
(CAN) WHILE IN CRUISE FLIGHT, PILOT NOTICED ENGINE FLUCTUATIONS OF APPROXIMATELY 150 LBS TORQUE AND 1.0 TO 1.5 PERCENT N1. RETURNED TO BASE WITH UNEVENTFUL LANDING. MAINTENANCE REMOVED THE FUEL CONTROL UNIT AND DISCOVERED THE DRIVE BEARING FELT ROUGH AND THE PLASTIC DRIVE SPLINE WAS SHOWING SIGNS OF WEAR/DISTRESS. THIS FUEL CONTROL HAD HAD A MID-LIFE INSPECTION AND DRIVE BEARING/SPLINE REPLACEMENT COMPLETED 80 HOURS PRIOR TO THIS EVENT. FUEL CONTROL TO BE REPLACED WITH O/H SPARE.