vacuum problem heat/4x4

I have a 99 jimmy slt. heater will only blow at you. no floor no defroster.4x4 is very difficult to switch in or out.
vacuum line in engine compartment found disconected. located between abs system and cruise cervo(electric). cannot locate any vacuum in that loaction to connect to. it seems some older models have a vacuum canister which clips to bonet, this truck has no canister and will not fit one in this location.
the vacuum line found does change things when pluged off but will not allow heat or 4x4 work if plugged before starting truck. when plugged it also changes the idle of truck.
any suggestions would be app.

Vacuum reservoir is in the left front fender, very close to the hood hinge. There is a check valve in the line to the reservoir, usually close to, and maybe behind the power brake booster.