The coolant hose connects to the bottom coolant port on the ISCV (Idle Speed Control Valve). There's another nipple on top of the ISCV which runs to the throttle body and then there's another nipple on the throttle body which runs down to the metal hard pipe assembly near cylinders 5 and 6. So... the hose in front --> ISCV --> Throttle Body --> the plugged hose in back.
What colors are the wires running to that connector? Given it's location and that the wires look red and/or brown I'd hazard a guess that it's for the EGR VSV; Should be mounted under the intake plenum toward the rear. See 25860 here:
http://www.cygnusx1.net/Supra/Librar...spx?F=1708&P=2