Are you tired of telling iTunes NOT to update to 3.1.3 every time you plug your iPhone in? Well, there’s an app for that. It’s called Fake 3.1.3 and it is ideal for people like me who don’t like being bugged by recurring iTunes alerts.
Fake 3.1.3 will make iTunes believe that you are running firmware 3.1.3, although you will still be on 3.1.2 with the older baseband. It kinda reminds me of FWchanger, although this one just helped make the App Store believe you were on a different firmware.
Fake 3.1.3 is available for free on Cydia via the http://cy.sosiphone.com repo.