I want to flash a new rom, but it will change my android ID. Is there any way to just back up my current android ID WITHOUT make a whole-system-backup?
Backup the "Settings Storage" app from TitaniumBackup. That will help you store your android ID. If you want to restore it, unfortunately, you'll have to use TitaniumBackup pro since it is the only app which lets you restore your Android ID.
Taken from XDA: