Thought i'd share in case others experience this as my dealership mentioned they've seen this before.. Car started stumbling and running extremely rough about 2 minutes into a drive, triggering it to go into Restricted power mode (limp mode).
We turned around and reluctantly drove it back to the house and had it towed to the dealer. After fearing the worst failure, my tech sent me the video of what turned out to be a dislodged metal reinforcement ring that sits inside one of the air intake hoses that are part of that center air intake assembly in between the two air boxes. It got stuck in the throttle plate, causing the mayhem that ensued!
Quick fix with a new intake assembly and reset adaptations and car running like new again, at 95K miles (2018 Si6)

 

This happened to my 2018 Si6 as well! it seems like a design flaw. If your intake assembly is approaching 100K I would recommend replacing it.