On my cylinder/valve/cam-shaft?? cover, there are two round metal caps (to the left of the engine oil filler cap). The rear cap (closer to the fire wall) had loosened (popped up a bit), was able tap it back down.

Does any one know how this cap is secured? Is there an o-ring or sealant used to secure the cap?

I've found what appears to be an oil leak down the back side of the engine near this cap and above the turbos.

I'm wondering its coming from this cap or I need to have seals/gaskets on this cover assembly replaced.