Universal Adjustable Pressure regulator
To maintain precise fuel metering, the vacuum modulated pressure regulator maintains a constant pressure differential across the fuel injector. This provides the fuel rail with a constant value of pressure above manifold absolute pressure.
Low intake pressure (when lifting off [deceleration]) pulls on the diaphragm which reduces the force that the spring can exert. This allows more fuel to return to the fuel tank which reduces the fuel rail pressure.
During acceleration, the throttle is opened and this increases the manifold pressure. This causes less vacuum on the diaphragm which increases the restriction of return fuel to the fuel tank. At this point pressure is increased in the fuel rail.
Connect the regulator using the connections as shown in the diagram