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 ON RIGHT ENGINE. AFTER DETERMINING PROBLEM ON RIGHT ENGINE, CHECKED LEFT ENGINE AND FOUND P/N LW10798 ADAPTER WITH SLOTS CUT LENGTHWISE IN SLIP JOINT AREA. SEVERAL CRACKS ENAMATE FROM THE END OF THESE SLOTS. REPLACED ADAPTER AND FOUND INTERCONNECTING PIPE P/N 78008 WOULD NOT FIT WITHOUT GROSS DISTORTION.