As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE IN STRAIGHT AND LEVEL FLIGHT PILOT REPORTED THE ENGINE RPM REDUCED SIGNIFYINGLY RESULTING IN POWER LOSS. AFTER A BRIEF TIME THE ENGINE RPM BEGAN TO OPERATE NORMALLY AND POWER WAS RESTORED. PILOT LANDED WITHOUT INCIDENT. TROUBLESHOOTING COULD NOT DUPLICATE THE PROBLEM.