On this model, are there serviceable check valves or crossover valves on the rack and pinion assembly that activate differently for left and right? Remember, the cylinder is filling for one direction and emptying for the other. There’s got to be something there.
(Thinks)
A quick look at Rock Auto suggests it is this $14.24 (US) part:
AC DELCO 19258114 Power Steering Control Valve.
Larry