I have one for my NX kit..but im alittle confused as to how it wires up. I know the red-power, black-ground, green-tach..but whats the other white wire coming out the other side hookup to?

 

Probably the relay.

Edit: If you can make a simple diagram of how your nitrous is installed I could tell you for sure. But if the other wires are hooked up right, then your window switch has to go to the relay (or it can go to your wot switch and then that goes to your relay but you get the idea) because when you're between x and y rpm's, it provides a ground for the relay and then sends power to your solenoids.

 

I'm running one on the Formula.. Yes, the white wire is your trigger output -- its all explained in the owners manual, but in short that wire triggers your relay (after going through your WOT switch, of course).