As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE ENGINE WAS RUNNING ROUGH LOSING 400 RPM'S AT LEVEL FLIGHT. ANY NOSE UP MOVEMENT CAUSED LOSS OF 300-500 RPM'S. THE ENGINE WAS INSPECTED AND NO FAULTS WERE FOUND. THE ENGINE CYLINDER COMPRESSION WAS GOOD (OVER 75 PSI ON ALL CYLINDERS). THE ENGINE WAS REMOVED FOR OVERHAUL.