As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE FLYING CRUISE FLIGHT NOTICED ENGINE OIL PRESSURE DROPPING. SHUT DOWN RT ENGINE AND RETURNED TO BASE. UPON INVESTIGATION FOUND THAT THE GASKET UNDERNEATH VACUUM PUMP DAMAGED. VACUUM PUMP CHANGED PRIOR TO FLIGHT. OIL LEAK NOT DETECTED ON RUN UP. GASKET P/N AS3491-01 REPLACED. AIRCRAFT GROUND RUN LEAK CHECKED OK. NO FURTHER DAMAGE FOUND.