What was found
(CAN) SHORTLY AFTER TAKEOFF THE PILOT OBSERVED TORQUE FLUCTUATIONS BEFORE THE ENGINE DROPPED TO IDLE AND THE PROPELLER FEATHERED. THE ACFT RETURNED TO THE POINT OF DEPARTURE WHERE AN UNEVENTFUL LANDING WAS ACCOMPLISHED. POST FLIGHT INSPECTION WAS ABLE TO REPRODUCE THE PROBLEM, UPON REACHING 3000 LB OF TORQUE, FLUCTUATIONS WOULD START AFTER 15-20 SEC. FOLLOWED BY DROP TO IDLE. TROUBLESHOOTING IS ON-GOING WITH THE REPLACEMENT OF THE FUEL PUMP.