Well, it sounds like you've got some vacuum issues if it's hard to shut off. I'd start looking there. A mityvac will help you isolate where this is (by plugging lines and seeing what holds vacuum and what doesn't)

The bad idle could be motor mounts (what does it do in reverse?)

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1982 240D, sold 9/17/2008
1987 300D TurboW124.133 - 603.960, 722.317 - Smoke Silver Metallic / Medium Red (702/177), acquired 8/15/2009
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