Well it's not a stock setup with the manifold and the vacuum lines
That was on a tee with the other line going into the firewall but when I had both lines hooked to the tee and one source from the manifold my air ducks in the car would change from defrost to the any other vents. I used my vacuum line tester and could build up pressure and get my vents to move. When I tried it on the mystery line I could never build up pressure. So that is either an open line or some large volume tank connector.
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