Here is a way to turn off ASD by coding without disconnecting anything.
Change the following FDL Code
CAF > 3000 ASD-Configuration - Funktionen - Baureihe to F021
Personally I still think you would be nuts to turn it off.
BTW, I have noticed the BMW exhaust gets quieter after break in, either that or US road surfaces and topology provide less sound reflection. However since I got the Eisenmann Sport exhaust my car sounds once again like it did in Europe - heavenly!