So, I purchased AD Delco 214-2147 off Amazon. Got it installed, but did need the jumper cable. Fortunately NAPA had one in stock. I got it all put back together and it drove fine. I filled up for the first time in weeks and the Hummer did stumble a bit after being put in drive and driving about 150 foot. The stumbling was not nearly as bad, it only did it for maybe 5 seconds and the tach only jumped from 500-750 or so. Very mild.

About a week later I filled up again thinking the first time was just the EVAP system cycling through. The Hummer stumbled again, much like the first time. After putting it in drive and getting maybe 200 foot away the tach jumped from 500-750 for about 7 seconds and then smoothed out, not issues since. I have about a half a tank and will fill up again this week.

Any thoughts on the issue still lingering (even though it is not nearly as bad)?