Many of the load-leveling equipped cars relied on that system to assist in maintaining static height, even unloaded. A slight sag could very well mean that the nitro cells are no longer holding up their end of the deal (literally). I was not aware of this until recently, and I have 2 cars so equipped.
Replace the nitro cells-simply can't hurt.
"If everything seems under control, you're simply not going fast enough" --Mario Andretti
1995 E500 street car
1986 Porsche 944 Turbo S track car