Download Custom Firmware For update iPhone 3GS Lock
Part 1 : http://www.mediafire.com/download.php?jvqy5d5ooc1cc13
Part 2 : http://www.mediafire.com/download.php?upy06w6xvuktkkz
Part 3 : http://www.mediafire.com/download.php?mf6j2bd11dxxdic
Part 4 : http://www.mediafire.com/download.php?k867by7y35wg0sv
Download redsn0w 0.9.10b5c fo DFU Mode
download : http://www.mediafire.com/?kgvxwqee34h1dhd

How to
1.enter your iPhone 3GS to DFU Mode to avoid iTunes error during restore
2.restore using iTunes please Shift+restore select sn0wbreeze_iPhone_3GS-5.0.1-9A405.ipsw
3.when your complete restore with Custom Firmware iPhone baseband doesn’t change.
4.enter Cydia and install Ultrasn0w from Dev team (http://repo666.ultrasn0w.com)
5.wait a few time you can see signal
enjoy.