As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNSCHEDULED LANDING WAS MADE DUE TO RIGHT ENGINE SURGING. EXAMINATION OF ENGINE REVEALED A 1 X 2 INCH SECTION OF DUCT WAS MISSING BETWEEN THE AIR BOX AND THROTTLE BODY. PART OF DUCT SEPARATED AND WENT THROUGH INDUCTION SYSTEM AND CYLINDER CAUSING TEMPORARY SURGING. REPLACED DUCT ON BOTH ENGINES. ENGINE RUN UP WAS NORMAL.