[truckster]

Originally Posted by cleszkie

Make sure that you don't have a kink/blockage in any of the low pressure return lines that run from the hydroboost and steering gear back to the pump reservoir. Sounds like you may be "starving" the pump. If the problem started right after you added the power steering fluid with stop leak, I would suspect that the stop leak may have reacted badly with the ATF and caused a blockage somewhere.

To add on to what Cleszkie said, stop leak works by causing rubber components to swell. In older lines that may cause blockage in the lines.