As a general rule, the SLS system should be flushed every two years....I found that out the hardway. It is not a well documented maintenance item.
The power steering pump may be a factor in the problems you are experiencing?
If the nitro cells have failed, you would feel it...very harsh going over things like Railroad tracks...I had a hydraulic ram fail and it was very noticable over washboard roads.
Get it in and take advantage of the warranty situation.
1992 500E Smoke Silver
2002 CLK55 AMG Cab Silver/Black
2001 Harley Fatboy - Pearl White
2004 F150 FX4 Silver/Grey
1969 GTO Liberty Blue
1956 F100 Black