Different Idles?

There's more to tuning than a rock solid AFR. I suspect it's in the tune to the extent that the tuner probably didn't spend much time tweaking the idle parameter options. These might be:
Hi Idle Car Speed X MPH
Hi Idle RPM Offset X rpm
Hi Idle Wait Time X Sec
Idle Off if TP over X %
Idle On if TP Below X %
Idle FB Above X rpm
Idle FB Below X rpm
Idle A/C Load Comp X %
A/C On Delay X Sec

I can see where a couple of these parameters can, if not set correctly, can cause an idle issue.

its called dashpot, sounds like it needs more low rpm pre position and the dashpot minimum mph clup disabled if you dont like the couple hundred rpm hang

has nothing to do with fuel

If the turner doesn't provide any help, see below...

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 134,000 hits, which indicates it does help fix idle problems quickly and inexpensively.