This question just occurred to me: On any old gasser engine that has had the EGR, air pump, and cats removed (basically all emission stuff), is it necessary to re-adjust the idle mixture - even if smooth running?

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Don't Chrome them; polish them

If you have anything for that matter that is working correctly is it necessary to "fix it" . I say leave it alone.

However, since post is a day old, I am to late if your an engineer.

Engineers cannot follow the rule if it ain't broke don't fix it.

Engineers live by the rule if it ain't broke, break it then make it better.

Generally no. However, by the late '70s - early '80s cars began using EGR operation to counteract any pinging, that might occur due to the advanced ignition timing and other adjustments that were adopted to try and improve performance and fuel mileage from the abysmal levels of the mid '70s.
If you're not experiencing any pinging or other performance problems, and aren't subject to emissions inspections, don't worry about it.

Happy Motoring, Mark

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DrDKW