If you have to just modify the iPhone 3G baseband to 2.28 without updating the firmware to 2.2 or 2.2.1, this is the easiest method to follow! The main reason for only upgrading the baseband to 2.28 is to achieve software unlock and still preserving all the jailbreak apps and appstore apps on the iPhone 3G. This has nothing to do with downgrading the baseband from 2.30 to 2.28 though.
Steps required in order :
1) Download ICE2_02.28.00.eep, ICE2_02.28.00.fls, BBUpdaterExtreme from this rapidshare link

2) Make sure your iPhone 3G is jailbroken and …