This is pretty advanced stuff that requires ibus hacking knowledge.

Basically you can change the levels that the Speed dependant volume control increase the audio levels in the ULF by using the following command. Currently BMW specs out the ULF to change the volume level up one notch every 40kmph, in 6 increments. That puts the max volume of the ULF at 240kph or 150 MPH.

http://www.bimmerboard.com/forums/posts/299773

here is the ibus string 3F 07 C8 09 02 06 28 0A cs default level of 40kmph steps. changing the 28 to lower numbers lowers the speed that needs to be reached to increase volume. around 20 might be better, but still playing with it

Martin