I have made several attempts at creating custom ipsw files to unbrick an iphone I have. Where I get stuck is when I go to iTunes and do a shift-upgrade, I get an error saying that my sim card is missing or not supported. I am using a TMobile sim card. Any ideas on how to navigate around this? Thx for the help....

In case you are thinking about replying, I have downgraded iTunes to 7.7. I can get the phone into DFU mode no problem. Shift-Restore starts fine, but now it gives me a 1600 error. I am going to read up on the 1600 error, but thought that might be useful info.

You'll need to use QUICKPWN / WINPWN to unlock the unit. If you don't want to do that, then you could always RESTORE with a custom made firmware that's already activated.

Yes! thats true you made your custom firmware but to install it in your iphone you gotta pwan your i phone first if you downloaded the custom firmware but if you created the firmware using pwnage tool or winpwn it would guide u through the process to get into dfu mode and get pwned so the u can shift restore your iphone!!