You've got a 26 year old car.
Lots of things can be neglected over the years, and usually are.

As these expensive cars are cycled through less discerning subsequent owners, many things are neglected.

Do a compression test, then move on the vacuum lines and tune up items.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles