I am trying to power my Nuvi57 from the USB sockets in my car in order to tidy up the cabling. However, the front USB sockets are also for data transfer so as soon as I plug the GPS in it goes into data transfer mode and won't allow navigation. I would like to be able to select NAV or Data mode when connecting to an intelligent device. Does anyone know if this is possible, if not can it be incorporated into an update?