85 K10 4wd relay

[JApple]

Trying to figure out the 4wd relay.  My connector is just hanging under my dash and I can't find the actual relay.  A PO probably removed it in the past.
It deals with k10 with auto MD8 & EGR bleed.   If anyone has any information on the relay I would appreciate it.  I would like to add it back if possible. My wiring is just like the diagram minus the actual relay.