My warranty is about up, so I had an independent shop do a full rubber glove treatment on the car to find any lingering warranty issues that I may want resolved prior to expiration.
I did mention the stumble issue, and he said he'd brainstorm a bit during the rest of the inspection on that.
Long story short, he smoke tested my engine, and found leaks at the intake tract at the boot and air valve. He reccomended replacing the boot, tract and valves.
BMW is working on it today. I could understand why a vacuum leak would cause irregular idling, so I'm keeping my fingers crossed!