Actually, the speed at which the suspension will go back to neutral is around 15-18 MPH. Take a look at the fluid for the hight control to see if it has been contaminated. The resevoir is located in the engine compartment forward of the passenger seat. I've heard reports of people mistaking this for a washer fluid resevoir and pouring wiper fluid into it. The vehicle should be in good condition at that mileage, the 90k service will be due soon. Depending on who you have do it, it will run around $1-2K. If it were me, I would check with Lexus to see if you can get any maintenance records, Lexus keeps them for all vehicles regardless of which dealer did the service. This will give you an indication of how well it was maintained.