are u running a bottle heater? if not that could be ur problem the nitrous has to be warmer than the temperature outside for the white mist to appear. as the bottle empties it just like a can of keyboard cleaner it gets cold and looses pressure but as soon as u heat it up it sprays hard again. same as a nitrous bottle. also if u dont already have a nitrous pressure gauge get one. i suggest getting the nx fire and ice heater/cooler to keep it at the right temp so u dont have any glitches in ur system, and will also keep the spray mist up if u just want to show it off.