How did you get your wife to pull the
oil pan? hopefully she is not parting out your car!! LOL
I'm guessing it was part of the intake valve. It could be cause by to much advance or detonation slamming that valve closed. KC likes to set 35 BTDC (most like around 32ish)
If it was the exhaust side I think you wolud have felt a major problem.
You might want to take a look at the piston head to make sure no damage has been done. Home Depot rents a sewer camera that fits in a spark plug hole. Sounds funny putting sh!t into your delicate combustion chamber but it works and you don't have to take the head, intake, exhaust off.