Intake Manifold Part Identification Help!

Here's the deal I'm doing PI swap and I'm modifying my PI intake to work with all the old hardware. The two sensors in the front were no problem but this brass fitting in the back is the issue. What thread size is it? And what is it even called? I can't find it anywhere. Ignore the arrow in the picture I'm talking about the fitting at the bottom right of the pic.

I was told its pipe thread but why would pipe thread have an O-ring? Any help would be appreciated.

For anyone who runs into this in the future I ended up just using a combination of hardware supplies and tapped 3/8 pipe thread in the hole and called it good. That thread size is not standard and that part won't fit in a PI intake anyway.