Diff lock inactive-still!

[Gfbourcier@aol.com]

Listers,
In the 87 4kcsq, the diff switch has 5 plastic vacuum lines running to it.  
In all but one line (orange) with the engine off, there is significant 
resistance to forced air.  There is zero resistance in the orange line.  
Attempted to follow orange line but lost it at the carpet at the firewall.  
Does anyone know where this line terminates/junctions with other vac lines?  
Should there be no resistance?
Thanks in advance,
Gil Bourcier
Columbia, MD USA
87 4kcsq-84k mi.