Help! 2017 SR5 5.7 Flex rpm stumble

So my truck has been acting up and can't figure it out. It got 67k on it, do alot of driving for work. It's got a very quick stumble in rpms around 1800 to 2100 rpm on light acceleration at highway speeds around 70 to 75mph. Noticed a few times on medium acceleration around 2800 to 3100rpm. My initial thought was bad gas but I've since ran 1 tank of 93 and a bottle of seafoam, took the throttle body off cleaned it, cleaned mass air sensor, put new filter in, and checked vacuum lines. No check engine light or issues with performance. Runs fine except for annoying stumble in rpm. Yesterday it only did it a couple times, this morning I filled up with another tank of 93 and it's stumbling like crazy. I fuel at shell and BPs when I can... Plugs or injectors or coil pack? Don't know what else it could be. Just tried sitting in parking lot and held throttle at 2000 rpm and tac will jump up or down 100 rpm or so. Any advice would be appreciated...

 

Around summertime there was a TSB for flex fuel software update. Some people said it fixed their problems. You can check via your VIN or take it to the dealer since still within warranty.