Donwload 3.1.3 : 4shared 

Here is a tweak which can be useful for the whole of users who want to keep their Firmware 3.1.2
Fake 3.1.3 is a free application from the repo Sosiphone.com which permit you to fake iTunes and then it will understand that you have Firmware 3.1.3

Notes :

• Reboot after install
• Works on iPhone and iPod Touch
• Installation