I have a jailbroken iPhone 3GS running iOS 5.0.1 with baseband/bootrom 05.16.02. I want to upgrade to iOS 5.1.1 but also make my device unlockable. With that baseband, however, I can no longer unlock my phone. I know I can install baseband 06.15.00 for the iPad WiFi+3G that Apple bundles with iOS 3.2 to 3.2.2 and then unlock, but that breaks GPS functionality.
However, according to this post it looks like it's now possible to go back to baseband 05.13.04 from 06.15.00, which still allows for unlocking. But I'm SOOOO confused.
So I install baseband 06.15.00 using a custom ISPW for iOS 3.2 to 3.2.2, jailbreak and unlock with redsn0w, then downgrade baseband from 06.15.00 to 05.13.04 while upgrading iOS 5.0.1 to 5.1.1 all with another custom IPSW, and then re-jailbreak?? Ugh!! My head is spinning!