[V8] Drivers side vacuum/something line, please help ID

[NIck Miller]

     I've got nothing to identify this with, and I can't seem to find its
partner :-(

I have a vac line on the drivers side that is disconnected.  I'm
entertaining the idea it COULD be a washer fluid line, in which case
everyone has permission to laugh, but I don't think it is.

The line is located along the drivers side fender, drivers side strut tower,
and behind the power steering reservoir, and under and to the outside of the
brake fluid reservoir.  It appears to go through the firewall bellow and
outside the brake res, and it goes to a "T" just before, maybe 4 inches, the
firewall.  This "T" has a dead line that points at the engine, but I can not
find where it should go.  I think this is causing my operating issues with
the car.  Some help would be appreciated!  thanks a ton!