can you identify these parts? aspiration 1985 520i -E28

http://www.jom.com.au/5F_1_car_enquiry.html
have a peek at the pic on this page see if you know what it is... I know it's a vacuum thingy, but what does it do?
how should I figure out how to adjust it?
actually I once mistakenly thought it would control the idle speed but it ain't that simple, and she idles a little wobbly (always has)
Basically I'm just trying to get this old girl to idle a bit smoother she is idling at 800 rpm, which is the recommended speed new plugs, new leads, air filter ok
it's a 1985 520i L-Jetronic E28 FUEL INJECTED
PART 1: PART 2: PART 3: PART 4:
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Looks like it's all part of the throttle control. The part A looks like a vacuum control for idle/emissions or cruise control (or both) not really clear what B is referncing; but possible a breather hose from the crank case C is part of the throttle D houses the throttle butterfly.

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