I am having the same problem at about 63k miles.
I ran several errands with the heat index over 105 degrees, A/C turned up all the way, 1/4 tank of gas left. Then as I was heading home (and flooring it going up some of our hills, like I always do), I gave it some gas and it felt like I was letting off the accelerator. I gave it more gas and it kept slowing down.
I literally had to floor it to get it to accelerate (it would downshift), but at the next light, it idled just fine. Tried AWD just to see what would happen - worked like normal, but still felt like I was towing a yacht. Turned the A/C off - no change.
Drive it today and it runs like normal again. No codes were ever thrown, but I'm assuming this was either a fuel delivery problem or the "limp home" mode, possibly triggered by ?? due to the heat?? Who knows?
The bad thing is - if it failed this time, it can fail again, and possibly at a worse time.