o you have the M102 - single OHC 8 valve engine, or the M111 DOHC 16V engine?
For European cars the M102 had a single chain, that tends to last 100,000 miles or so but gets noisy.
I'm told that the double chain fitted to the 16v M111 engine lasts longer.
W124 94 E200 Wagon M111 engine 103K miles
used to have a 87 200T wagon M102 engine 150k miles.