MBWorld.org Forums - Harsh ride? W211 Wagon. Any idea?

Hello. (Excuse me if this have been covered before or if placed in the wrong thread.)

I´ve owned my 2007 W211 E280T wagon facelift model for some months now, and I´m just about to get used to the car´s charasteristics. It´s a great car! However I think that the ride feels slightly harsh on all kinds of roads here. Going over speed bumps in lower speeds the car feels great and firm in a good way, but when the road gets a little rougher I can feel every little pothole and road joints and I´m jumping around in the drivers seat and road noise is also little too evidental, wich could drive me crazy - This is not how i Merc should feel?

I´m just wondering what could cause such a stiff ride. I guess something is not right here.

I test drove a very similar E280d wagon Avantgarde on 18" wheels with the same suspension system the other day and it had a completely different feeling. It swallowed every roughness and pothole much better.
I´m currently on winter tyres becaus I live in Finland (and I drive an EU model car) 205/60/16" with correct tyre pressure so that´s obviously should not cause any rough ride. About 140.000km on the odo now and shock absorbers never changed as far as I know of, (still no visible oil leaks in the front). OEM suspension with the self levelling air struts only in the back (no airmatic). Back end for certain deflate over the weekend but inflate properly when the car is started again. Ride height is fine and no broken levelling sensors or linkage as far as I can see (maybe worn out tho?). The car is a Elegance trim but since it is a "facelift" model the dealership told me I have the slightly stiffer Avantgarde chassis?? (Sorry if I`m misinformed). I will soon be up to shearch for any air leaks, but I think leaks could not be the reason why the car have a hard ride??

I believe my rear suspension struts have no external accumulators, just an electric pump that keeps the pressure at level when the car is on. I´m no expert in these suspension systems so excuse me if I might be wrong somewhere. No squeaking or clunking from the suspension, just an annoyingly overall harsh ride. I´ve been trying to find something on forums and some say that some kind on accelrator sensors located under the passenger seat could be faulty and some say that the electrical connectors to the rear struts must be disconnected and cleaned, but I have no idea if whese advices are relevant? Could worn out front shock absorbers cause a harder ride or may it be the slightly leaking rear struts that put the whole system out of play? Did read about a guy who changed his Avantgarde shock absorbers and springs to "softer" ones from a Classic trim version and got a much more comfortable ride. Don´t know if that´s an option for me but I certainly want a more comfy ride in my Merc. Hoping you guys maybe could have some tips for me.