What was found
(CAN) WHILE PREPARING FOR THE SCHEDULED NIGHT FLIGHTS, AFTER NORMAL ENGINE START, WHILE RUNNING UP TO PERFORM THE FEATHERING CHECK, THE ENGINE COULD ONLY ACHIEVE 1700 RPM ON THE PROPELLER WHERE 1900 RPM SHOULD HAVE BEEN AVAILABLE WITH THROTTLE FULL FORWARD. FLAMES COULD ALSO BE SEEN ON ENGINE SHUTDOWN. TROUBLESHOOTING LED TO THE REPLACEMENT OF A FAULTY FUEL CONTROL UNIT.