Dean...Didn't you see the "Nitrous Experts" thread...Why aren't you installing your own system??? Installed my own system, and I never..even..learned..to..read!!!
The fuel safety switch works perfect for me, in fact, the "ground" supplied by the fuel safety switch goes through my "window switch", and between 3000 and 5500, the "window switch" grounds the N20 relay...pretty neat!
I suspect a bad ground in the previous post, or maybe that little valve was left in the fuel rail, or most likely they just needed to buy one set at a lower volume, or an adustable fuel safety switch, these are cheap enough and in a wide variety through Summit, Jegs, etc...Not specific to NX Express or NOS, they all pretty much work/look the same...
How big a shot are you going to run??? I think I will be the second person to tell you that I honestly don't think you'll need the controller...If you really feel you need something, maybe a "delay" would be the way to go...Either way, controller, delay, or just your right foot, keep us posted!