HELP, Flex fuel “surge” when engine is cold

New member and new tundra owner. Even though I’ve read a lot from this group being a non member. I have a 2014 tundra 5.7 flex fuel. I’ve read about hard starts, ecu, surging under load, and fuel pump issues. My truck has no issue starting. But usually on my first drive in the am it will “surge” at high rpm around a shift point. It will only happen once on my drive into work as soon as I leave house. After that it runs great with no issues for the rest of the day. Usually has to sit for 7+ hours for it to happen again. I’d appreciate any advice on resolving this issue. Can provide additional information if needed.

 

Sounds like cold transmission fluid.

 

I was thinking something with trans fluid too at first. Maybe low? Just replaced fluids in front/rear diffs and transfer case yesterday. Have 12 bottles of toyota atf on porch to replace that this weekend and ensure level is correct.
However, the way it surges, I’m thinking it’s something else. While slowly accelerating, the surging feels like I’m giving it throttle then letting off over and over. It will just hang there in that rhythm until I let off gas.

 

I can feel it. Feels exactly like I’m pushing on gas pedal and letting off (getting fuel, then not) over and over… even though I’m holding pedal still

 

just an update. did a fluid transfer using the oil cooler lines and fluid must have been low. took out 11 qts and added back 12 qts, but when i checked fluid at temp there was no trickle. so added one more quart and did fluid level check procedure again and got a slow trickle out of check plug so called it good. hasn't done the surging once since then which has been about a month. thanks for the replies