Mystery vacuum 2004 navigator 4x4

[mills1447]

During an 8th cylinder spark plug replacement, I still had a lingering black, hard line vacuum that naturally sits in the general area of the power steering canister and the air intake tube...it is a secondary line to another vacuum that connects behind the radiator which extends back towards the firewall of the driver's side.

 

[AWAR]

That is the vent for the IWE on the driver’s side. Mine still has the split loom covering and is attached to the front brake line at the master cylinder