As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED LOW MANIFOLD PRESSURE IN-FLIGHT ON RIGHT ENGINE. INVESTIGATION SHOWED THE LEFT EXHAUST ADAPTER P/N LW10798 CRACKED AT MOUNTING FLANGE. REPLACED WITH NEW PART AND FOUND INTERCONNECTING EXHAUST PIPE P/N 78008 WOULD NOT FIT WITHOUT GROSS DISTORTION.