The schader valve is before the regulator which means that it is subject to the same pressure at the injectors inlet. It should rise when the engine is running, and you disconnect the line from the regulator. When the line is reconnected it will fall with the level of vacuum.
Going forward a cheap and easy way to read codes and data if you have an android phone is the BAFX elm327 Bluetooth module and the Torque pro app. It allows you to do anything a code reader can do plus monitor live data like O2 voltage, timing, injector pulse width and almost anything you can dream of all for less than $30. That gives you a lot more data than just watching pressure from the gauge.
Jeff
