[FRED]

In your hand is a NON TURBO boost sensor (Mazdas words from the FSM) or if you will the pressure sensor. Ain't no MAP sensor.

It should be seeing vacuum from the intake manifold.

The NON TURBO pressure sensor in your hand will give a false reading to the ECU and the idle will be a bit crummy because of that.

Disconnected from a source of vacuum that non turbo sensor will send to the ECU a voltage close to what is fuel cut i.e. 3.65vdc is fuel cut on a stk car. The FCD connected to it is preventing the ECU your using from going into fuel cut.

That sensor being disconnected is outputting just what the FSM says. See JPG below and the figure for pin 2B on the ECU of a stk NON TURBO (remember that 327 in your hand is non turbo).

The second jpg shows what a TURBO sensor would output under the same conditions i.e. vacuum hose off the sensor. Quite a difference in output, right?

Get a N318 sensor for your series four Turbo car.