Yes, so i've heard, which is also why I looked for a path to A/T.

But the modulator has its own vacuum outlet from the manifold, i.e. it does not come via the vacuum distribution block. And the modulator vacuum line does not seem to have oil in it. Anyway, it would be against the stream to pass oil from one vacuum outlet on the manifold to another.

The vacuum distribution block has a non-return branch connected to A/T vacuum reservoir and to the two switchover valves mentioned. And there is clear traces of oil in the line leading to the valves and in the black/red line leading from one valve to the A/T. I can only see that it goes to somewhere on top of the A/T but not exactly where.

So, does anyone know what it does, and how I replace the leaking part (whatever it is)?