As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED FATIGUE WHILE FLYING. NO OBVIOUS EXTERNAL SIGNS OF MUFFLER FAILURE WERE FOUND, SHROUD REMOVAL REVEALED A TIGHT CRACK FROM NR 2 RISER INTO BODY, 3 INCHES LONG THAT LEFT VERY LITTLE STAINING ON INSIDE OF SHROUD. MUFFLER BODY WAS DEFORMED WHERE RISER IS WELDED INTO BODY, NEW MUFFLER HAD NO DEFORMATION IN THIS AREA.