The KCA-420i module that I've installed in the M5 does not wake up the iPod from hibernation by default which means that if I leave the car off for more that 16 hours, I have to get into the trunk and manually wake up the iPod. This is somewhat inconvenient since I normally don't realize this until I've already started driving away. Fortunately, someone has developed a chip that can be added on which will resolve this. Here are the links to the various places with information about it.
Intravee Homepage
Intravee Forum - Problem Description
Intravee Forum - Modification to wake up iPod from Deep Sleep
Intravee Forum - Additional KCA-420i modification information
Chip Installation Directions