Downgrade 3.1.3 MC model to 3.1.2 and jailbreak.

This is how to downgrade ipod touch 3.1.3 mc model.

First) Download 3.1.2 IPSW. (search on google)
Second) Connect your ipod touch to your computer
Third) Click on "Summary" then press Shift then click restore (Mac users Option restore)
Third) Browse for the IPSW, then press open.
Fourth) Then it will do its thing.

Good Luck! Type in the comments if you had any problems.
P.S The most reliable source to download the IPSW:http://www.felixbruns.de/iPod/firmware/

The Jailbreak
This jailbreak is tethered for MC models. This means you will not be able to shut the ipod all the way off or let the battery die without having to reconnect with Blackra1n.
First)Go to blackra1n.com
Second) down below the image of geohot with the flying iphones, there will be two images, one of appple and another one of windows. Click on the image that represents your Computer software.
Third) A download will automaticly start.
Fourth) Plug your ipod to the computer
Fifth) Run blackra1n and click the big "Make it Ra1n" button.
Sixth) An image of Geohot will appear on your ipod, now just wait untill it does its thing.
Seventh) When that is done, it will go to the lockscreen, just slide to unlock, then swipe a page to the right. there will be this black drop on the left top corner.
Eighth) Tap it, you will see cydia and rock, tap both, then press install.
Ninth) Reboot your ipod, by slide to power off.
Tenth) Turn it on, you will see a restore logo, do not restore, but click the make it ra1n button again.
Eleventh) You will see this "Rock your Phone" logo from rock installer.

You are Jailbroken! Congratz!

PS Blackra1n was not made by me, all credit about blackra1n goes torwards Geohot.