Bump to this thread. I know where mine attaches; a nipple on the intake manifold right next to the one for the check valve that comes off the vacuum solenoid (that also connects around the valve cover to the emissions vacuum pump).

But back to this vacuum hose--how do you replace it? Mine has disintegrated. Does it just pull off and on here at the firewall? It feels like it goes some distance through this little port into the firewall, and I am afraid that pulling on it will just leave a bunch on the vacuum port on the firewall that I cannot get off.

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2001 E53 3.0 5pd