I know these is a popular topic, but it seems like there is a simple way this would work. Can I use Pwnagetool to create a custom 3.1.3 firmware (already JB) and simply restore to that? Or do I have to restore to original 3.1.3 and then do the jailbreak?

I also need to unlock the phone, is that possible with the baseband 5.13.04?

Thanks.