I have this old 1990 W201 190e 2.3
I've had this old Girl for about 5 months now, so far not too many issues considering the age of the car and the purchase Price ($1020 NZD, with 163,000km (102,000 miles).
Recently I noticed a smell of raw fuel coming through the air vents after a decent run, I searched on this forum and soon found the problem was likely the EHA valve and thought I should join up.
So I just purchased a second hand EHA unit from Ebay for around $79 USD, comes with new seals, 30 day warranty and claims to be fully tested.
This is the state of mine, you can see the residue around it.
Annoyingly I broke the hose that goes from the Valve cover to the air filter, however it was perished and worn out anyway and previously cracked.
When I got the car the Heater blower motor wasn't working, at first I noticed the fuse was blown, I changed this, it blew again straight away, so the next step was to remove the blower motor and de seize it with lots of penetrating fluid, 4 months later its still working, albeit a tad noisy at times.
The fan belt was loose also, but this turned out to be the mini shock absorber looking thing that had gone bad, so that was straight forward to sort out.
In the near future I need to investigate why I can occasionally smell that sweet coolant type smell when using the heater (goes after after about 20 seconds or so) I suspect the heater core has a small leak, which will get worse with time.
This car is pretty much the Daily Driver, my project car is a E30 325i
In comparison the MERC offers a much higher level of Refinement and Ride Quality and feels somewhat stronger then the E30.
The E30 is a lot more of a drivers car and is rather fun to drive.
Its interesting having 2 cars the same age as a direct comparison is fair.