My 2003 Cadillac CTS has 4 vacuum hoses at the rear of a plastic cover on top of the intake manifold. You can see them near the beginning of this video The mechanic leaves the cover dangling from the tubes I'm asking about.
I'd like to know where they go and what they do. I've looked online for a diagram or other explanation, but apparently I don't know enough to formulate a good Google query.
