As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT EXPERIENCED LOW MP AT 22K. SLOWLY BLED DOWN AT CRUISE. PILOT SAID AT NORMAL 25 INCHES, IT BLED DOWN TO 22 INCHES WITH FUEL THROTTLE. UPON CHECK MECHANIC NOTED EX STAINS ON R/CYL BANK AND DISCOVERED FLANGE COMPLETELY SEPARATED AT TURBO FLANGE AREA EXHAUST MANIFOLD. NEW PART ORDERED AND REPLACED.