As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THIS AIRCRAFT HAS A TURBO NORMALIZING SYS INSTALLED UNDER STCS SA10588SC & SE10589SC. THE FAILURE OCCURRED IN ONE OF THE COMPONENTS INSTALLED WITH THE STC. DURING A 500 HR IN SERVICE INSPECTION IAW SI11-01, IT WAS DISCOVERED THAT THE LT EXHAUST MANIFOLD WAS CRACKED. THE CRACK WAS LOCATED ON 2 SIDES OF THE RECTANGLE SHAPED TUBE WHERE THE TURBO MOUNTING FLANGE IS ATTACHED. THIS MANIFOLD IS OF AN OLDER BUT STILL COMMON DESIGN.