you have a turbo or supercharger on your car? did you install it yourself, or have it installed? and how much did it cost?

About your problem Ive got a theory on the accelerator sticking. the added pressure of running boost is holding the butterfly valve open not allowing it to return to idle, this happened to my when I was tinkering with my lawnmower and a 12v blower, i couldnt get the mower to throttle back without lowering the forced air input from the blower.

about the hard starting, when last did you do a thruough tune up on the car, replacing plugs, wires, distributor cap, rotor, air filter, and fuel filter.

about the other problems ive got no ideas and am definately not qualified to give any oppinions as i have never experienced my tach going to 0rpm with the engine running, my car doesnt have ABS so i cant help there either

hope what I did know a bit about helps out

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1984
190e 2.3L
107000 miles