2015 GMC Acadia Denali Engine Flare (Transmission or Sensor?)

[snailstampede]

I've been trying to diagnose an engine flare that happens between gears 2&3 and 3&4. I've got about 75k miles. 2015 Acadia Denali.

I had my transmission fluid drained and checked at my local GM dealer. The trans seems perfectly fine.

It happens every day more distinct some days. On really noticeable days, I'll even have a rumble as I'm driving down the road. As if I'm driving over rumble strips.

As of now, I'm looking into my throttle position sensor as a possible contributor to the problem because I do have a rough idle as well that seems random.

I've already replaced a few other things but right now, I'm curious if my throttle sensor needs replacing. Check out this video and listen carefully. Is a throttle sensor have loose pieces that rattle normally?

https://youtu.be/Xafp8z_0ezs