I tried earlier today, I have the IPSW and iTunes did not allow it through Shift+Restore. It would check the file but would stop before loading it on to the phone. I know there is no real reason to doing this but I've been having problems with connecting to AT&T with the phone. I can call and text but data/internet is not working. I'm getting the "Could not activate cellular data network" pop-up when I open safari. I've done countless restores to backup and even setting it up as a new phone.