I am trying to downgrade my ipod touch to firmware 2.2.1 from 3.0, but I hear that it's impossible. I am wondering how to put it in pre-jailbreak mode (white screen) so I can restore with a custom ipsw in iTunes. Is there a terminal command I can use on my mac? Or is there an app just for doing that? Has anyone successfully downgraded their iPod (not iPhone)?