The 93 ls 400 that I have owned for about 3 years now have always been much more sensitive in steering than the 92 ls 400 that we have owned for 5 years. Neither show any signs of steering trouble in general and there has been no change in either during the time that we have owned them.

In practical terms it seems that you have to pay more attention to the driving in the 93 as the steering seems too sensitive, there is little if any feedback from cornering etc. The 92 gives a firmer response with definite corner "feel". If I had a choice, I would like to have the 93 behave like the 92.

Does anyone know why there is a difference and what if anything can be done about it? Would appreciate any imput.

 

I have a 92 that feels the way your 93 does, or at least that's the closest description I've heard. I thought I had fixed the problem by correcting tire pressure, and that helped considerably, but the car still seems to require too much attention to drive. There is virtually no slack in the steering, but there is a horrendous creeking from the front right when turning, especially at lower speeds.
Sorry, this didn't really answer any of your questions, but this is the first post I've seen with problems very similar to my own. I do recommend checking tire pressure though. I got a lot of input earlier about the suspension bushing and shocks, just haven't had the time to act on any of it.

 

......forget that worn out BALL JOINTS can also contribute to sloppy steering (lack of straight line stability on the freeway). Incorrectly performed alignment (not enough positive caster) can also cause "nervous" or "darty" steering when driving in a straight line.....besides, the LS is notorious for lower ball joint wear.....that's why I will be replacing my lower ball joints when I install new Air shocks shortly!!

 

Lexus changed lots of things - bushings, larger tires and wheels, etc. - between the 90-92 and 93-94 LS400 even though they look a lot alike. An 1989 Automobile Magazine article (it compared the LS400, Q45, 535i and 300E) criticized the early LS400 for its somewhat sloppy steering. Hard to believe I kept a magazine for almost 17 years!