The 190D's didn't have any electric engine controls until the '85 MY when they switched over to electric idle control from vacuum controlled. The engines are largely mechanically controlled though.

I would suggest you read some of the good Doktor's posts on the matter as he owns four 190D's and is most knowledgeable about them.

Here are some links
http://db.mercedes.cx/mb/200002/24/0003.html
http://db.mercedes.cx/mb/199812/04/0017.html
http://diesel.mbzarchives.org/2000/Feb/Vol_3_Num_98/ (19th post down "Questions: new to list")

Good luck in your search!

Chris