Nitrous pressure should be kept consistent to obtain optimum performance. All NOS systems are designed to work best with a bottle pressure of 900-950PSI. Pressure is determined by the amount of nitrous contained in the bottle and temperature. It's a good idea to use a bottle heater and/or blanket to maintain predictable performance levels when racing. Likewise, maintaining consistent line filling is important, which is why racers use an NOS purge valve to release nitrous vapor from the feed line. This provides liquid nitrous to the inlet of the solenoids for better consistency and repeatability.