The models with two vac ports, one above the other, should have a vacuum hose from a continuous vac source on manifold routed to the thermal vac vavle on cyl head near the #1 intake runner. The hose then should lead to a "T" fitting and the hose to the bottom port should have a vac check valve installed in it with the hside you can suck through pointed towrds the "T". The other side of "T" should have a vac hose that goes to the other port. When cold the Thermal valve is open and vac passees through. When you accelerate the vacuum level drops but the trapped vaccuum under a diaphragm onto which a regulator spring rests will pul that diaphragm down and the control pressure will drop which richens mixture for improved throttle response. When coolant temp gets warm the thermal valve closes and this fun is over.