I need to replace the thermo vacuum valve on my 1980 924 and I am unsure as to how to connect the vacuum lines up as the replacement is not the same as the original. It has two vacuum ports that are isolated from each other when cold and connected to each other when hot. One of the ports has a slight leak when cold but not when hot. I think this port with the leak should go to the back side vacuum advance on the distributor but am not sure can anyone help?