Working on a 2001 3.0 after swapping the heads and having hell trying to find a diagram that shows where this other line goes. I know one goes to the fpr, I've got the evap, egr, egr control solenoid, and the reservoir plumbed in. Any help would be appreciated

 

Looks like the vacuum line for the inside duct work...supplies vacuum to operate the vents. May lead to the vacuum storage ball first. You can use regular 1/8"ID rubber line to replace or make splices. As you can see the hard plastic lines can get brittle over time.