The most common cause of that code is the intake boot. The small part of the hose in the back will crack in the folds. Smoke is reverse pressure it could easily push the crack together. Basically the crack can act like a heart valve letting air in but not out.

You can spray carb cleaner near the area and watch the O2 sensor readings but just poke with your finger. Once you can no longer see part of your finger (because it's inside the boot) you've found the leak.

I had three invisible 1" wide tears in my intake boot by the time I got the same code.

No idea how it ends up on one bank maybe the IAC vents into bank 2.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)