I had a similar issue with my bimmer it turned out to be a throttle body issue in which my throttle body was literally sealed shut. I would suggest you start with clearing your idle control valve and throttle body if you haven't done these things yet. Please continue to post your progress so the board can attempt to help you guys!
V/R Zachary Pullins Sr.
National Capital Chapter BMWCCA
NCC Member Recognition Chairman
NCC High Performance Driving School Registrar
NCC Auto-X BOD Liaison
DIY Senior Committee Coordinator
2006 E90 325Xi & 2000 E46 3XXi
" Vision without resources is just hallucination"