Your engine probably cruises on the main jet circuit, If so, then the cruise A/F ratio will be set primarily by the main jets.

The idle mix and off idle transitions will be set by the Idle Fuel Restrictors and Idle Air Bleeds. And although these circuits overlap in use, they are 2 different jetting exercises. There is another thread running now that is into this.

In my experience, the only real way to get the cruise ratio where it needs to be is with an O2 meter. The idle however, can be dialed in with listening to what the engine likes.

That is because most of our engines like 14.4-14.7 +/- cruise ratio. And I don't know how you would achieve that by driving and listening. The idle mix however is very different combo to combo, and is usually best set by what the engine combo likes.

And although there are recommended guidelines and starting points, the initial timing and the timing curve is another area where experimentation with what the combo likes is often the best thing.

Even EFI set-ups on engines with more cam overlap are often locked out at idle and settings are fixed.

On my engines, the bigger the cam, the more idle lead they want. I have 25* advance at idle on the engine in the Cuda.

IHTH