As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED LOSS OF MANIFOLD PRESSURE AFTER TAKEOFF. MADE OFF-AIRPORT LANDING. NO INJURY, NO DAMAGE TO AIRCRAFT. MAINTENANCE INSPECTION FOUND ALTERNATE AIR DOOR HINGE PIN MISSING WHICH ALLOWED THE DOOR TO FALL INTO THE CONNECTING ELBOW TO THE TURBOCHARGER RESTRICTING AIR FLOW.