That is correct...it is the line that was running under the drivers side of intake. Goes to the Y fitting on the IMRC's back of intake.That video does not apply for your application.
http://www.mustang6g.com/forums/showthread.php?t=33556
Check post #24.
I believe the line you're asking about is the IMRC vacuum line. Leave it running into the dirty line on the driver's side.