As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED LOW OIL PRESSURE AT IDLE, REMOVED OIL PRESSURE REGULATOR AND FOUND SHARP METAL CHIP IN BOTTOM OF REGULATOR WHERE IT HAD ARRIVED AFTER FALLING OUT OF REGULATOR SEAT. PREVIOUS EXPERIENCE LED US TO BELIEVE THAT THE METAL WAS FROM A LIFTER, WE INSPECTED ALL 12 LIFTERS AND DISCOVERED A SEVERELY SPALLED EXHAUST LIFTER ON CYLINDER #4. INSPECTED CAM IN ACCORDANCE WITH CONTINENTAL SERVICE BULLETIN SID05-1B, INSTALLED NEW LIFTER AND WILL INSPECT CAM AND LIFTER AGAIN IN 100 HOURS (AS PER THE SID).