I am dealing with BMW of South Atlanta.
Do you have more info on the SIB for this? Is there a SIB number or description?
South Atlanta said nothing was on the books for the GT on this.
My 2011 GT also does this after it has warmed up and the sits for a short period.
You are correct the idle can surge up to 1100-1200 rpm. Not sure what would happen if you dropped it into gear at that point.
I am attempting to get a video on my BB before service on 7/24.
Sorry you are fighing same issue but good to hear I am not the only one. Surprising we are the only ones with this problem.
2011 535i GT Alpine White/Black
Sport/Winter/Sound/Conv/Nav/Heads Up/Rear Shades/Rear Camera
1979 911 SC Porsche Targa
2004 Volvo XC 70 - Lady car
1999 Sea Ray Sun Deck
2001 22' Party Barge Pontoon