All the above. I would place a bet, that the DISA valve is also bad and sucking air. My kids drove the snot out of my 2003 x5 3.0 5-sp. since 2008. I finally made it my daily driver. Multiple codes.............. Positive smoke test. bad idle O2 codes, etc.
Replaced plugs, started using non ethanol fuel, repaired the DISA valve, replaced the Post cats. O2 sensors. and Voila. all codes were gone. She runs like a top. My 2 cents.