Vacuum leak?

When I turn my steering wheel to the right I hear what sounds like a vacuum leak. That is I hear a hiss. I discovered it when sitting at idle. When this happens I notice the rpm's drop slightly.

1987 Laredo (yes it has cruise)

Any thoughts?

TIA
8700XJS

I would think if you had a vacuum leak your RPMs would go up not down.

To me it sounds like the steering pump. On almost every jeep (every vehicle for that matter) I've owned if you turn the wheel all the way to one side or the other it will sound like it's 'hissing' and the RPM may drop just a hair. Granted if the PS pump was going bad it would start to squeal most likely BUT in my opinion it sounds like nothing is wrong.