So when replacing my valve cover due to a bad pcv today I noticed it came with a small plug that fits into the back of the pcv. Does this serve a purpose, and what might that be?

Yes plugs into valve cover where the red hanging hook/delivery hook is located. Once the red hook id removed you put in the plug./cap

Yes, just pull the red hook and replace it with the plug in the bag.

https://www.northamericanmotoring.co...lve-cover.html