Ongoing issue with numb steering at speed

[1991 Corvette ZR-1]

Hello all. I have had my ZR-1 for a few years now and one thing that has always been present is the loose steering feel. I have replaced the loose factory rag joint with a solid aluminum disc and also had the rack rebuilt by Turn One. I also rebuilt the factory power steering pump. No difference in road feel. The car feels fine at highway speeds up to about 65. Anything above that with WOT and the steering feels very numb and does not inspire confidence. I only have two other options that this could be:

1) somehow, I was charged a rebuild fee for my rack but it was not rebuilt. I did note that the exterior had not been cleaned / sand blasted as they have done for another rack I sent them years prior.

2) The tilt sphere assembly in the column is worn and WOT shifts magnify the disconnected steering feel past 65 mph.

I am going to say it is number two, as the column is up there in age and it may be time for a rebuild. Has anyone experienced what I can only describe as numb disconnected steering at speed? I feel like I have touched everything possible that could be causing this but the column. Upper ball joints were replaced not long ago, while the lowers still appeared good upon inspection.