I have an iphone 3gs 4.0.1 firmware. It is starting to crap on me so I need to upgrade it either to 4.0.1 again or maybe to 4.2.1. It is jailbroken right right now and unlocked on the 5.13 firmware I believe. Its the one where it doesn't screw up your gps. I would like to upgrade to 4.2.1 while preserving the baseband. How would I go on to do this? I know I will need to use a program to preserve my baseband and another one to allow me to upgrade a ipsw that is old. (I do believe I have the SHSH saved in surik server since this phone was jailbroken for about a year)