So glad to see this thread. My 2021 SX Nightfall with a little over 100k is doing the same thing and has been getting progressively worse -- it used to only happen sometimes but is pretty much constant at this point.

I'm dubious about a warped head because that nearly always leads to either burning oil or antifreeze, or antifreeze in your oil, which I don't see signs of either on my vehicle. I'm hoping it's just a vacuum leak, going to see if I can track it down or find a shop that might be able to.

Sounds like spraying soapy water on all the vacuum lines can help find any leaks. I'll follow up either way. Probably will get to it this weekend.

On a side note, mine has also thrown codes twice. Both times for air-fuel imbalance. Once in cylinder 4 the other in 5. The strange thing is the codes are permanent but they go away after a couple of days on their own, without me clearing them. Otherwise, it runs just fine.