As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MUFFLER/HEAT EXCHANGER END FLANGE SEPARATED FROM THE MUFFLER HOUSING CAUSING LARGE AMOUNTS OF EXHAUST TO ENTER THE CABIN. PART TT: 1,711.4 HOURS. MUFFLER MIGHT HAVE BEEN REPAIRED BY WELDING ON THE OUTSIDE OF BOTH THE FLANGES. SUBMITTER SUGGESTED NEW STYLE MUFFLER OR REPETATIVE INSPECTIONS.