Goodjob finding the culprit.

FWIW..500 is a little low...Correct OE spec is 650rpm +-50.
Check the idle control hoses and if they are rock solid, replace them to avoid future potential roadside issues. They are incredibly important hoses and eventually crack causing massive vacuum leaks. A 1/4in tear will cause a non-running condition.

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2016 Monsoon Gray Audi Allroad - 21k
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