From another forum (not tried this myself yet and not sure if for e85 with nav)
Adjusting the speed sensitive Audio volume setting
1. Turn radio off and then on.
2. Press an hold the "SEL" button.(I believe for like 10 seconds or so)
3. Radio will display the software version.
4. Use the "<>" button to go thru the settings.
5. Find one that says "GAL"
6. Use the "1,2,3,4,5,6" buttons to change the value (1-6, 1 is lowest, 6 is highest speed volume compensation)... you cannot set it off.
7. Turn radio off and then on.
There are several hidden resets with this vehicle. Windows, adaptive throttle, etc. Most of which have been posted here, which is how I got them . I'll try to post them in a seperate thread.