So I think I finally figured out the problem to the rough idle I've been having as well as my stalling: a non-working fuel pump! Even though I rigged up a light to the fuel pump wires, it was not an accurate test. I disconnected the ground wire to each pump one at a time and turned the key to the on position and heard the buzzing of one pump. When I tested the other pump it was dead silence. Since both pumps are about 24 years old I decided to bite the bullet and order 2. I will see what happens and keep this thread updated once I change them out.

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1990 190E 3.0L