As you may have heard, PwnageTool 4.0 was released today. Thought I would make a thorough video of creating a custom firmware for your iPhone 3GS. Remeber, PwnageTool is only for older bootrom iPhone 3GS, that has already been jailbroken.
Make sure your SHSH (AutoSHSH) is backed up to Saurik’s server and make sure you do an iTunes backup, as well, before attempting to restore with your custom firmware. You don’t want to mess something up, and be forced to do a clean, official restore, with no way to come back.