No rpm gauge?
Personally, I would adjust the rack until it idles evenly, then you can lean it out, to the right idle speed if need be.

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

Other than a cheap optical reflective tachometer. If the automatic transmission is not pulling at idle. You are probably good to go.

Reason alone suggests that time and wear alone can modify the original idle speed of these engines in service.

so ..

1. adjust rack damper to stop shaking

2. adjust idle so the car does not move forward on idle?