From my recent firsthand personal experience, Chitown offered up some very sound advice:
1.) Learn what you can what may have happened from the forums or an independent BMW only shop, don't necessarily believe the dealer.
2.) KINDLY (don't lose your cool too much) push the issue with the dealer and BMWNA if needed. You paid a surcharge for a CPO.
3.) If all else fails get a quote from a BMW independent shop.
Re-read this thread. Be prepared and let them know you are very ready to move to option #3 listed above. This, I found, was crucial to my success during negotiations. An independent mechanic can be very important leverage - and be prepared to spend the $$ to get closer to the truth. The dealer and BMWNA does not want this!!
Do not accept the first, second or even third offer. See option #2