The iPhone Dev Team has updated ultrasn0w to “Ultrasn0w 0.93” which can be used to unlock 05.13.04 baseband. So if you have updated your iPhone 3GS firmware to iOS 4, then your baseband would be upgraded to 05.13.04 ad you can use ultrasn0w 0.93 to unlock your iPhone 3GS.

Ultrasn0w 0.93 Important Points

• UltraSn0w 0.93 can unlock baseband 05.13.04 and older basebands 04.26.08, 05.11.07 and 05.12.01
• Ultrasn0w 0.93 can unlock iOS 4 firmware.
• iPhone 3GS owners (If used Spirit for first Jailbreak) should stay away from iOS 4
• Your iPhone must already be jailbroken.

Procedure to Unlock iPhone 3GS on iOS 4 and 05.13.04 BB With Ultrasn0w 0.93

1. Launch “Cydia” and go to “Manage” section present on the bottom of the screen
2. Touch on “Sources” and then on “Edit” and finally on “Add”.
3. Add the Cydia URL as repo666.ultrasn0w.com and touch on “Add Sources”.
4. Once the Source is added to Cydia, hit the return to Cydia button at bottom of the screen and then Done button
5. Now search for “Ultrasn0w 0.93″ and install it.
6. Once the installation is completed just reboot your iPhone 3GS and it will be unlocked!

Once your iPhone 3GS on iOS 4 with 05.13.04 Baseband is unlocked you can use any SIM card of your choice.