2004 Mazda 6, 2.3l kicking code P2187 Bank 1 (as if there's any other bank) lean at idle

I’m currently being puzzled by this vehicle. Any simple solutions out there for this simpleton?

Look for a vacuum leak.

That’s pretty much what I was thinking, too, although the car seems to run pretty smooth. I researched it a bit, and a likely culprit may be the MAF sensor. Seems like every time I run into this code on a Ford, it ends up being PCV related, with the car idling bad.