As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT IDENTIFIED HIGH MANIFOLD PRESSURE REQUIRED AFTER TAKE OFF AND PERFORMED A PRE CAUTIONARY LANDING OFF AIRPORT. INSPECTION REVEALED A WET SPARK PLUG ON CYLINDER # 6. AFTER REMOVAL OF THE VALVE COVER, A BROKEN INTAKE VALVE TIP WAS DISCOVERED. NEW STYLE ROTATOR CAP INTAKE VALVES ARE INSTALLED PER LYCOMING SI1280D.