As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE MUFFLER TAILPIPE IS CHAFING ON THE FIREWALL. A WEAR SPOT WAS FOUND ON INSPECTION. THE ENGINE WAS GROUND RUN AT AN OPERATING TEMPERATURE WHICH CAUSED THE MUFFLER TAILPIPE TO EXPAND UP TO 13 MM CAUSING IT TO TOUCH FIREWALL AT FRAME NR 1. SUBMITTER RECOMMENDS REPOSITIONING TAILPIPE DOWN MORE TO PREVENT THIS DEFECT.