Yes, it does terminate inside the cabin.

It is used as a vacuum bleed down. The VCV uses less vacuum as the rpm increases. Clean air inside.

Usually the shift points are controlled by the Bowden cable. It is adjustable. On top of the cam cover is an accordion covered cable. There is a white nut at the top, adjust that. The other end connects to the transmission.

EDIT: Appears as if it's time for a brake fluid refresh.

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83 SD

84 CD