I am chasing a demon. I have a jumpy idle while in drive. This occurs predominantly with the AC engaged. The MAF is good, the throttle body is new along with the the TPS and IAC that came attached to the throttle body assembly. I've checked the AC charge and it is ok, I did this thinking it may be low causing a random draw causing an idle increase. There is a little bit of noise coming from the idler pulley but nothing wild sounding. When running the scan tool the lowest the Throttle Position % goes is 18 and on average it hovers around 18.8, then during the noticeable jump it goes to 19.2 or 19.4. I have put high octane gas, fuel treatment thinking it was bad fuel. So, the idle change is a jump not a drop. I'm left scratching my head. There is some hesitation on take off too. Any ideas?

This is happening on a 2007 Yukon XL 5.3 129,256
And when the erratic idle happens the variance is approximately 100 rpms 553 - 449

Turns out it is the driver side motor mount. Which makes sense because it only stumbles while in drive.