I have been using a jailbroken iPhone 3GS on OS 3.1.2 for a long time. Recebtly I decided to wipe my iPhone and install firmware 3.1.3 and then jailbreak and unlock my phone.

Well, as you all know it is not possible to unlock on the firmware 3.1.2. So know I would like to downgrade the firmware to 3.1.2.

I have read numerous blogs on how to do this: I have edited the hosts file in notepad ( gs.apple.com), but when I put the iPhone in DFU mode and then selected to restore the firmware to 3.1.2 it came up with: gs.apple.com

Also, I did not save my settings with Cydia when my OS 3.1.2 was running.... does this make a big difference?

I therefore do not know what else to do. I have an iPhone which is currently unusable. I would be eternally grateful if someone could guide me to being able to downgrade the firmware of my iPhone from 3.1.3 to 3.1.2.

Thank you so much.