Buscas algun custom firmware 3.1.3, Conectas el iPhone en modo DFU y presionas SHIFT y cliqueas restaurar, lo buscas y lo restauras, te va a dar un error cuando ya va a finalizar, luego con el tinyumbrela lo solucionas. Si tienes la basehand 06.15 con iOS 4.1 lo puedes desbloquear de esta manera:
Es super facil, a mi me funciono. PS. Te recomiendo que dejes el 3Gs con el 4.1, si tienes la basehand 06.15 desbloquealo con el video que aparece aqui, funciona perfecto, solo hay que seguir paso a paso. Aqui esta en ingles: We will be using DiskAid to access our iPhone Contents. iPhone used in this video was iPhone 3g running iOS4. You can use whatever Client you use to access iPhone Contents, like iPhone Browser on Windows or Phone Disk on Mac. You will be needing Ultrasn0w deb file. Download it here: http://www.megaupload.com/?d=WC12TWLP And if you need DiskAid Download it here for Mac & PC http://www.digidna.net/products/diskaid/download IMPORTANT: In order to Unlock your iPhone 3g or 3gS on 4.1 or 4.2/4.2.1 you will first need to change its baseband. To change your iPhone's baseband you need to use Redsn0w 0.9.6b5 . This Redsn0w 0.9.6b5 will change your baseband to 6.15.00 and then you can Unlock. How to use Redsn0w 0.9.6b5 Video Link
When you have opened DiskAid then you need to transfer the *.deb files that you downloaded from Ultrasn0w zipped file, put them in var/root/Media/Cydia/AutoInstall. If the Cydia/AutoInstall directory is not there, then you create one as demonstrated in the video. NOTE 1: Type Cydia folder with UpperCase "C" and AutoInstall folder with UpperCase 'A' and 'I". Once all above is done as shown in the video, you need to restart your phone couple times, the 1st for Cydia to install the packages and second time Ultrasn0w start to work. Done. NOTE 2: If you are stuck on Apple logo on second boot due to your own Tethered Jailbreak. Then use Redsn0w 0.9.6b6 to boot. Put iPhone in DFU mode and run redsnow with option 'just boot tethered right now'.