Make iTunes Believe You Have iPhone OS 3.1.3 Installed
It wont be long before some newer apps from the iTunes App Store will require you to have the latest iPhone 3.1.3 firmware in order to install a particular app. Earlier this month, Apple released the new iPhone OS 3.1.3 for iPhone and iPod touch which upgraded the baseband to 05.12.01 for iPhone 3G and iPhone 3GS, hence making it impossible to unlock them on the latest firmware with the newer baseband.
If for some reason you have decided to hold off from upgrading to this minor update until the new iPhone OS 3.2 or iPhone 4.0 is available, you can fake your firmware to iPhone 3.1.3 which will make iTunes believe you have the latest firmware installed, hence allowing you to download and install all the apps from the App Store.
Simply follow the steps below to fake your firmware to iPhone 3.1.3. This wont in any way effect your baseband/unlock or anything in real. All it does is change the version number from iPhone 3.1.2 to iPhone 3.1.3.