Just bought a 3gs w 3.1.3 and 5.13 baseband. I unlock/jb already. I am on windows...dont have access to a MAC. I want to UPGRADE to 4.x.x firmware. TU and Cydia wont save any SHSH on this phone anymore...it only saves 4.2.1 and up. What are my option to get it to 4.x.x firmware without shsh blob? This is a firmware UPGRADE and not downgrade...so i was hoping it;s possible without shsh blob.