I bought a really clean 1991 300e (175k), but it has a few issues.
It was sitting for two years so Im pretty sure it needs a fuel filter, although the acceleration cut out and sputtering issue seems to be getting better.
Ignition parts all seem to look new, except the coil.

The main problem that is a major annoyance is the Alarm. It is an aftermarket set up, and its been draining the battery. I try unhooking all 4 wires that are tapped into the fuse box, the alarm still works, but now I cant turn it off, or start the car. So I have to leave them all wired in and it doesnt make sense. Also, unlocking the door doesnt not deactivate it, i have to turn the key and push a button under the dash. Stupid.

Couple other issues Im not happy about, its a bit sluggish and the engine sounds like its out of a dump truck, minus the turbo. Just loud straining sound. My 89 was quiet and clean.
Also I hear a bit of rattling from my timing cover. Could the chain be stretched at 175k?

Any feedback is much appreciated, cheers.