As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MECHANIC WAS PERFORMING MX ON THE AIRFRAME AND NOTICED EXHAUST STAINING ON THE OUTSIDE OF THE COWLING. ON OPENING THE COWLING THE MECHANIC DISCOVERED THE EXHAUST HAS BEEN PRESSURIZED AT EVERY ANNUAL SINCE INSTALLATION. THE CRACK WAS NOT EVIDENT AT THE LAST ANNUAL APPROX 90 HRS AGO. IT WOULD APPEAR THAT THE CRACK WAS CAUSED BY EXCESSIVE STRESS ON THE EXHAUST.