I found this in a couple of minutes in the CD. It is under climate control vacuum diagram. It is the line that goes right on top of the box to the center vacuum servo. The servo is for the cold air blend flaps.
(The cd told me this. I don't have this stuff in memory)
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM
[This message has been edited by Benzmac (edited 08-26-2000).]