This is most likely a sticky hydraulic valve lifter (sometimes called a valve tappet). The hydraulic (non-adjustable) lifter replaced the old-style adjustable lifters where high pressure oil is pumped into the lifter to take up the slack between the valve and the cam.

The idea is that hydraulic valves/lifters are always in perfect adjustment - except when the lifter sticks and won't take up the slack - then you hear the valve tapping on the lifter because its out of adjustment.

To fix this, the cam cover has to be removed and the lifter repaired or replaced. This job is actually more complicated than it sounds because the cams need to be locked in place so the engine keeps timing and so they don't fall out when the cam cover is removed. Also re-sealing the cam covers can be a pain (there is no gasket, just sealant). When you're ready to learn all of the details you can do a search and find all you need to know. Its not an immediate need, but its also something that shouldn't be forgotten.

Best post of the week! :D :D :D

Thanks so much for your help.

I'm not sure what I'm looking at here. Is that a rock inside the bearing race?

No, that's a broken piston and its associated cylinder bore !!
The darker grey half circle located just below the broken piston crown is the piston ring.
It shouldn't look like that......
If your IMS bearing collapses, the piston and valves can collide and cause damage as in the picture

Another option is to do nothing. The early dual row IMSB, up to around 2000 had very low failure rates, less than 1%. The problem is that for MY 2000, there is no really reliable way to determine if you have the dual row bearing or the single row (that has an approximate 8% failure rate) without taking out the transmission and flywheel.

I have a 2000 with a build date of June 1999, so I am fairly convinced I have the dual row bearing and I'm not going to do anytrhing until I have to replace the clutch.