Just replaced the power steerring box in my 66 Satelite.
Was primarily for a leak. but also partly due to how it drove . It seemed to dart around a bit on crappy roads

Just drove it and noticed drives a little better but has a noticable difference in the assist in required effort from left to right . I dont remember if it had this before or not

Turns left super easy,,,, but requires a good bit more effort to turn to the right . Not manual steering effort but definitely more than the opposite direction

Jacked it up think I had a valve off center .
But started it up and steering wheel stays rock solid in the center while up, I turned the steering wheel and I can notice an effort difference even while jacked up in the air with both front wheels hanging

My brother's Malibu has a similar issue, turns out one of the power steering hoses had a kink in the hard line. Not sure why it only showed up in one direction, but it did.

Could be a bunch of things so go thru the checklist. Binding somewhere, hitting something, interference, something bent or busted, problem inside the box, suspension issue, ball joint issue, etc.

Effort should of course be the same turning in either direction.
I'll assume you've bled the system, as you said the steering wheel stays straight when running with wheels in the air.
If it changed with the box, that would seem to pinpoint the area of the problem.
As far as being darty, I'd expect that to be an alignment or even a tire problem, if not a rutted road.
If one or more of the bushings has deteriorated, the steering and/or suspension settings are moving as you encounter variances in the road surface, right ?
I've also had that happen with square-shouldered radial or bias-ply tires on rutted road surfaces.

Yes. Its been a while since ive driven this car.
But don't remember this issue before. Just the darting around like something binding in steering. Car didnt want to return to center atfter making turns on its own.
Main reason replaced the box was leak...and this darting around.
And making adjustments to the box made zero difference or made it worst.

Entire front suspension is supposed to be new...like under 5000 miles..
I bought this car as is ( its my yellow one) But plan to take it to work and ck it out on the lift.
Ill look thru paper work and see if alignment sheet was printed out.

GTX, there is a valve at the top of the box where the pressure line attaches. It’s a plate with two mounting bolts. If you loosen the plate bolts the plate can slide a bit…which makes a BIG difference in how the steering pulls one way or the other.
You adjust this with the wheels hanging in the air, engine idling. Many people don’t know about that adjustment.

Im familiar with the adjustment you mention.

Ive had the front in the air and running. ...it doesn't turn .

Nor does it pull driving down the road

Watch the steering wheel when you start the engine, if it moves even slightly that valve needs to be adjusted.

When adjusting that valve body (on top of the gear box), I highly recommend not just having the front wheels off the ground, but to have the front wheels removed from the spindles. You want as little friction (weight) as possible so to assure the power assist of the left-right-left-right action is at a minimum of the gear box.... IF you wanted to go a slightly different and better route, you could alternatively disconnect the Pitman Arm from the steering link cross-arm (letting that hang)... again, reducing all possible friction from the gear box. That's how I've done it in the past... best results!