Thank you all for your much appreciated input.

Just to clarify regarding the seats, my wife doesn't merely complain about lack of comfort, but more seriously about back pain... But I'll try your suggestions, and hope that we don't need to sell the car: after the money and effort invested to correct all the previous owner's backed up maintenance, it would be a shame...

Regarding the mileage:

* It seems possible then to get better than 20 miles / gallon in mixed driving. Which is what I am still hoping given that, if the W124/M104 Wagon's weight is (to my recent discovery and surprise) in fact comparable to the W126/M103's, its engine is supposed to be more modern and efficient? So I'll double-check all those plugs, wires, etc., thanks.

* Since the car tends to be sluggish going uphill, I thought that the transmission might be slipping and explain the possibly subpar mileage. But a specialist checked it and gave it a clean bill of health. He did however confirm my symptoms, but pointed me instead to some play in the throttle linkages, and maybe engine management tweaks. But I understand that nothing can be tweaked on an M104? He did show me the play in some of the throttle linkages, he just didn't know if they were normal (he is a transmission expert, but doesn't do too many MBs). Additionally the W124's throttle isn't as progressive as the W126's (which is now butter smooth :-) ).

So the question is: Can a W124/M104's throttle be as smooth and play-free as a W126/M103's? I am thinking that it may also help with the downshifting going uphill, the lack of which may explain the current sluggishness?

Looking forward to your further input, this forum is great!

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1991 W126 300SE (M103)
1995 W124 E320 Wagon (M104)