You need a drop pitman arm for 6” lift….I’m no expert…but I had the same issue. Your drag link needs to be level, it makes a big difference.
I Replaced ball joints,
Jeep steering shaft,
Red head steering box,
Dual steering stabilizer's,
Still wandered,
It looks like I had the same pitman arm as you only difference is I have 4” lift, swapped it for a 4” lift drop pitman arm. I wish I got that first it made a huge difference.
Someone tried to fix the problem by tightening the steering box that’s why it doesn’t return to center.
(I also did that) I don’t think these trucks lifted steering will ever be perfect, heard crossover steering works pretty good haven’t tried it yet
Hope this helps…