So many attempts at this question without a clear answer and if there were one buried somewhere it should be a sticky.

Can I upgrade from 2.2 to 3.0 and yet retain my baseband 2.28? If so, how? If this already exist, please make it a sticky.

You cannot do that. On 3.0 FW, only baseband 4.26.08 works. Baseband 2.28 and FW 3.0 are incompatibles

You can always prevent a baseband update with PwnageTool by making a custom IPSW but there is no point as 3.0 cannot function with the baseband from 2.2 so you will have a glorified iPod Touch.

The unlock code in ultrasn0w is the same as the unlock code in yellowsn0w the only difference is the way the unlock code is injected into the baseband. If yellowsn0w/2.2 works for you then ultrasn0w/3.0.1 will almost certainly work also.

Simple, clear answer, as has been given many times befoer:

NO

But why on earth would you want to?

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