Any Pontiac guys on here? Need insight.

So, after doing some research and speaking with Butler's Performance it seems the lifters are probably the oiling issue. Butler's gave me a couple things to look at to confirm this. The little disk inside the lifter that I was questioning may just be the culprit. These disks are supposed to be able to allow oil past them to go up the pushrod and oil the valve train not completely block it off. They can have holes in them to accomplish this but, the ones with out holes should be stamped with a small arc to them or, have small area that is notched or, bent up to allow oil out of the inner chamber. If the valves were set too tight, over time it can flatten out the disk there for completely blocking the flow of oil out of the chamber. I have a couple more things to look at to confirm this but, I feel like this is forward progress on getting to the bottom of this.