I think I've got it!
Glad to see I'm not the only one scratching my head over this one!
After doing some detective work in the repair CD, I bet you've got automatic level control. If so, you have a "tandem pump" in which the power steering pump and the level control "oil pressure pump" are driven by a common shaft. Do you have a separate oil reservoir under the hood? If so, you've got level control. That would explain why a pressure line would originate from around the PS pump and head towards the rear of the vehicle.
I don't know what to make of your symptoms, but I did see in the CD-ROM a nice algorithm for checking out the system. It's in section 32-0501 in the Chassis and Body CD.