Hi guys, i have a 3gs running 3.0 , and i would like to upgrade and still be able to jailbreak. I've been doing research... i read somewhere its not possible to upgrade to earlier firmwares, because apple isnt signing them anymore. So what are my options???? I had this phone for a while, so it may have the old bootrom i need to jailbreak from 3.1.3 but im not sure. ANy HELp ??