As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER DEPARTURE PILOT EXPERIENCED SLIGHT NG FLUCTUATION AND SLIGHT YAW MOTION. PILOT RETURNED FOR LANDING. DURING TROUBLE SHOOTING MAINTENANCE OF THE ENGINE FUEL CONTROL UNIT, MAINTENANCE FOUND INSIDE THE ACCELERATION CONTROLLER CHAMBER THAT THE LOWER CIRCLIP WAS MISSING FROM FROM A LEVER PIN AND A SPRING FROM THE PIN WAS DISENGAGED FROM THE PIN. FUEL CONTROL WAS REMOVED FROM ENGINE TO BE SENT TO REPAIR SHOP.