Jailbroken iPhone upgrade IPSW to 3.1?

[BossBoz]

I have a jailbroken phone running 3.0.1 which I jailbroke via redsn0w. In some posts, it seems like you can run 3.1 if you use a proper IPSW (one that doesn't come from Apple)? Is this correct? If so, where can I download the appropriate file and what do I do after downloading the file? Thank you.

 

[wivelden]

Same here... On v3.0 and want to update to 3.1 keeping the BB at v4 and unlocked.

 

[mwg3c]

Ditto for me. How does this work?