Originally Posted by MaxxRPM
That's a heat sensor. It just screws into the head but not into the cooling system. Atleast that's the way it is on the PI heads. I can't image it being any different on the NPIs. I'd take it out and look in the hole just to be sure. In fact, there should be the same hole on the other head (that one will be towards the back) and won't have anything in it.
Looks to be like you said a heat sensor, its too far away from the cam.
I will check my old head and see whats in the back of the hole it has to be a plug thats threaded in or something to block it off.The RH head does have the hole like the old heads do. I saw the wire going under the intake and was curious to what it was for.