I have a 1998 Lexus LS400, with a little over 80k miles.  I had the shocks and struts replaced by Lexus, and still notice a "floaty" ride, especially on bouncy sections of the freeway.  It almost feels like the car is still undulating after going over the bumps.  If you have ever ridden in a mid-1990's Nissan Maxima, you will know this feeling.  Its almost as if each shock is working independently and transmitting different "ride feedback" to each corner of the car, if that makes any sense.  I took the car to 2 Lexus dealerships, one did the "bounce test" and told me the rear shocks dont seem as good as they should (even though they were replaced by another dealership).  The dealership that DID replace them says nothing is wrong with the car and a Lexus does not ride as stiff as a Mercedes or BMW.  I am aware of this, but really if all the LS models ride like THIS car (I only had the car a year, so not the original owner), I am surprised they should ride this LOOSE.  Or maybe they do ride like this, since they are a big car and rear-wheel drive?  Any suggestions or comments?