What was found
(CAN) ACFT EXPERIENCED NR 2 TORQUE AND PROP FLUCTUATIONS ON TAKEOFF. ACFT RETURNED TO DEPARTURE. LANDED SAFELY. DURING THIS EVENT THE NR 2 ENGINE WAS SHUTDOWN AS A PRECAUTION. (CONSIDERED TO BE A NON BASIC IN FLIGHT SHUTDOWN) FOLLOWING THIS EVENT PCU WAS REPLACED. A TEST FLIGHT WAS CONDUCTED WITH NO FAULT FOUND. A PIECE OF LOCKWIRE WAS FOUND IN THE OIL RETURN PORT OF THE PCU. A TEARDOWN REPORT OF THE AFFECTED PCU WILL BE OBTAINED.