What is this and do I need it?

NOX , was a emmisions control device. That is part of the circuit that warned you when you were stepping on the gas to hard. It would flash the drivers side fender mount turn signal to warn you, your heavy on the throttle. It tied into multiple things. Look at your speedo cable there will be a large cylinder just below your brake booster with a single wire going into it as well. That was part of the system also.

My suggestion remove it all. Its just not worth the hassle to get it to all work properly.