I called BMWNA and elevated it at my dealer's suggestion, since my dealer's last attempt to fix it with a reprogramming that did not take all that long, did nada. BMWNA told me to make another appointment with the dealer and that service would coordinate with BMW engineering on fixing it. The dealer called and said that he would get me a loaner (I asked for a 6 Series convertible - but no dice). He did say that I should expect them to have the car a few days.
Let's hope that this second attempt to fix it works since I too am worried about seeing someone's grill getting larger in the rear view mirror and feeling that helpless feeling as I push in 3/4 throttle and get nothing but lethargy in response.
2012 535ix Space Gray, Cinnamon, SAT, Premium, Prem sound, Cold W., Sunshades, Gloss Black Grille, Gloss Black Side Markers, RE970AS 245/45/19 non-run flats that run very smooth + quiet and also correct the otherwise optimistic speedo