Hey there, long time haha. I have spoken to some buddies over time and from what I have found. Swapping to an n/a power steering pump after the hicas delete should fix the hard steering. Thereโs another post on twin turbo net talking about signalling issues that would also cause the issue.
http://twinturbo.net/nissan/300zx/forums/technical/view/1164091/Power-steering-assist-speed-signal-and-hard-steering-Long.html