Where Does This Pictured Hose Go?

[BimmerM3inGA]

I'm in the middle of replacing the head gasket on my 2001 X5 3.0. Technically, I'm redoing the job after somebody else screwed it up royally. I bought the car this way and have no idea who did the work last time.

To make a VERY long story as short as possible, whoever did the head gasket last time made a lot of mistakes. There were a bunch of missing and/or incorrect fasteners, missing parts, and disconnected fittings. I've managed to figure out where everything goes, except for one little hose.

This was already disconnected when I disassembled the engine, so I have no reference to go by (I labelled everything that I took apart). In fact, I didn't even notice it until I got ready to start putting everything back together.

It is a small rubber hose that is connected on one end to a fitting in the firewall between the two hoses for the heater. The other end is just dangling and there aren't any obvious fittings within its reach.

It is highlighted in green in the two photos. If anyone can identify it, I would be most grateful!

[pezho405]

on my 4.4 that part is actually plugged up. ive looked on realoem for yours and didnt find anything

[BimmerM3inGA]

I didn't find anything, either. Nor could I find it in TIS.