Yes you can downgrade the firmware.
http://vwnavi.com/showthread.php/11563-Downgrade-Question-from-2660-to-1100
You could also run a modified version of a newer f/w that will not give you battery drain. The choice is yours.
http://vwnavi.com/showthread.php/11563-Downgrade-Question-from-2660-to-1100
You could also run a modified version of a newer f/w that will not give you battery drain. The choice is yours.