As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE RAN ROUGH IN CRUISE. CARBURETOR HEAT HELPED SOME. REMOVED PLUGS, FOUND TO BE RUNNING LEAN. REMOVED CARBURETOR, DISASSEMBLED AND FOUND ONE PIECE VENTURI LOOSE IN UPPER CARBURETOR PIECE. SUBMITTER SUSPECTS AIR BYPASSING VENTURI AND CAUSING LEAN MIXTURE WEAR ON VENTURI AND UPPER CARBURETOR PIECE IS CONSIDERABLE.