They have wot switches for a reason. Just spraying any time you want can be unsafe. Like if you spray under 3000 RPM's, there's a good chance nitrous can puddle in your intake, and perhaps detonate. I used a window switch, I had the juice start at 3200 RPM's and stop at 5800 RPM's. That way if I missed a shift and banged off the rev limiter (6500 RPM's) The engine wouldn't cut back timing and fuel, lean the engine out, and possibly throw a crank through the block.