VW bus

Does it look like kind of a cone shaped thing, with an adjustment screw on the back (remember back is toward the rear of the car) and a threaded shaft with an adjusting nut, going to the throttle?

If so it's a throttle valve positioner. An emission control device, which allows increased air to enter the carb when you lift the pedal. It supposedly reduces emissions.

It was on most '68 and '69 1500s, and all '70 and '71 1600s.

I just pulled it off and plugged the vac line on mine. (I know, I don't care about the environment, I'm a polluting pig, yadda yadda yadda)

In any event, it was froze solid and didn't really do anything. You can do without it.

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It's probably a previous owner. Or did you mean something weird in a mechanical way?

-Bob Hoover

Sounds like a vacuum-operated throttle positioner - yes it is smog-related.

You can remove it with virtually no ill effects. It might possible be causing a fast idle, if the shaft is frozen, but I would look to more normal causes first...