had something similar....
my check engine/emissions light came on.
dealer originally changed a o2 sensor, but light came back on.
car was escalated to special tech team- they found 2 leaking injectors on left cylinder bank.
SA submitted PUMA case- ended up replacing all 8 injectors and spark plugs.
all good since then.
2011 550i : Alpine White l Black Dakota l Anthracite wood:M Sport pkg l Sport Trans l Active steering l Conven pkg l Driver asst pkg l Prem pkg 2 l 4 zone AC l Side/Top view cameras l HUD w/6wa ext blk pnl l BMW Media adptr /apps l M Decklid Spoiler l Clear Bra l V1 Radar; Ordered 4/9/11, Delivered 5/21/11
-2008 550i MSport: deep Sea Blue/ Black, Loaded
-2005 545i : Silver Gray/ Auburn, Loaded
-1993 3215iA : Jet Black/ Black, Loaded[/FONT]