How to Downgrade Your iPhone 3G 2.30 (2.2.1) Baseband for Unlock

These are instructions on how to downgrade your baseband from 2.30 to 2.28 for iPhone 3Gs with the 5.8 bootloader. This will allow you to unlock your iPhone 3G using YellowSn0w. An similar exploit is still be worked on for those with a higher bootloader version...

IMPORTANT: Make sure your iPhone uses the 5.8 bootloader before continuing. You can find instructions on how to check your bootloader version here :
https://www.youtube.com/watch?v=dmeArx...

Ensure you are on the 2.30 baseband by following this tutorial.
https://www.youtube.com/watch?v=yLblaD...

You will also need MobileTerminal installed to completed this tutorial. you can download this from cydia.