No clue what was up
Went under to finish up a couple spots and noticed where the trans support had snagged my temp band exhaust spot (where the front pipe and muffler mate) had come a little lose and there was some exhaust blow by.
So I redid that and drove to the parts store... No sleeping engine.
Drove it a few times since and no issues.
I can't imagine the blow by changed the back pressure (goes into 2.5" straight pipe) enough to cause the issue.
But since fixing that, the Jeep gods have smiled upon me and ...
She's good now