As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER PERFORMING AN ANNUAL INSPECTION WHICH INCLUDED CHANGING THE VACUUM SYSTEM CENTRAL AIR FILTER, THE ACFT DIVERTED FROM ITS FLIGHT PLAN TO MAKE A PRECAUTIONARY LANDING DUE TO A HORIZON GYRO FAILURE. FOUND ONE OF THE LATEX TUBES USED AS A VACUUM LINE IN THE LATE MODEL MOONEYS HAD FOLDED OVER RESTRICTING VACUUM TO THE HORIZON AND CAUSING THE HORIZON TO FAIL.