bad fuel? just a guess...
try having the injectors cleaned... that may help... I think somebody here just did...
07 650i Cabrio CPO, Titanium Silver
Black Matte Grill
Dark Birch Wood Interior and Shifter
HUD, Cold Weather and Sports Package
Logic 7 Sound
Aluminum Racing Pedals
K&N Air Filters
Rays Master Piece REM 20" Forged wheels w/ Conti Extreme DWS