I need education on the Thermoquad "staged accelerator pump" , that gives an additional shot when the secondaries open

Pretty sure all the 9XXX TQs had a ported vac adv port. Because the VA was switched to manifold vacuum via temp switch if the engine got too hot. The EGR port looks similar to the VA port, but not quite the same position. VA port is on drivers side, EGR on pass side.