NA steering issues

I'm putting my problem out there as I'm now at my wits end with it. hopefully someone can think of something I haven't.
My NA wanders, badly. It pulls left and right seemingly at will. Under normal or hard acceleration, braking or just cruising. It also pushes away from any king of bump or side to side undulation. Even putting a wheel on a thick painted white line will push it hard left.
The pull is not like you'd expect from say worn TREs where it wanders and I have to correct, it comes all the way through to the wheel. Almost like an invisible man sitting in the passenger seat pulling the wheel about.

The confusing bit,,, wishbones, droplinks, TREs, inner TREs, springs, shocks, top mounts , rear subframe bushes, rear ARB, trailing arm bearings, wheel bearings and bumpstops all new 6 months ago.
I've checked and re-checked every bolt, pushed and pulled and levered every joint and can't find play anywhere.
The tracking has been set and checked twice ( by different garages) tyres are premium brand with good tread and correct pressure.
I don't know what else to do.

Power steering system?

I'm hoping someone can tell of a problem with the PAS pump or rack that would cause those symptoms. And how to test either. Cause I'm stumped

Were all the above parts changed at the same time? Did the problem appear before or after changing those parts?

Have you used a torque wrench on all replaced bolts to be 100% sure they're OK? Were new bolts used or just the old ones? Also check front subframe bolts.

If you used crappy Fiat wishbones maybe the threads have stripped.

All except the wishbones were at the same time. They were about 3 months before but still only done 5k. I can't remember the brand but checked ball joints and they're still tight.
It's hard to tell if it was there before as all the above mentioned components were in terrible condition and I changed so much in one go.
I've checked front subframe bolts and wishbone to subframe bolts. All good. This morning I'm changing the upright bolts and ball joint pinch bolts as I'm doing the cv's so might as well. Might flush and replace the PAS fluid while I'm under it.

Just got back from fiat dealer with genuine pinch bolts and upright bolts.
6 nuts and bolts,, £40 !!!
I feel like I've been raped

Ok i just found something interesting. The new upright bolts from fiat are exactly 1mm thicker at the shaft. Not due to corrosion either.

Play in the steering column uj?