If you have an iPhone 3G and you have this feeling that upgrading to iOS 4 has slowed down your device and that you want to go back to iPhone 3.1.3 / 3.1.2. Or if you are one of those iPhone 3GS (new bootrom) or iPod touch 3G / 2G (MC model) user who has upgraded to iOS 4 only to find out that you cant jailbreak it can follow the instructions posted below to downgrade iOS 4.0 to iOS (formerly iPhone 3.1.3 or 3.1.2).
