Ported Vacuum Control System (1.6L, 2.2L & 2.5L 4-CYL)
As throttle blade opens, a slot type port in the carburetor throttle body is exposed to an increasing percentage of manifold vacuum. This port is connected through an external nipple directly to the EGR valve.
The flow rate is dependent on manifold vacuum, throttle position and exhaust gas back-pressure.