EGR Valve
The vacuum diaphragm chamber of the EGR valve is connected to vacuum port in carburetor flange through backpressure transducer and thermal valve on most models.
As throttle valve is opened, vacuum is applied to EGR valve. When vacuum overcomes EGR valve spring force, it opens EGR valve to allow recirculation. On Impulse turbo models, manifold vacuum is applied through the vacuum switching valve.