it won't let me restore back to 4.3.3
pker886, i may have solution for you. i was in the same boat as you, i bought an iphone 3gs with 4.3.4 baseband 5.16.02. Of course i don't have SHSH to restore older firmware.
I was able to upgrade the baseband to 6.15.00 by playing with redsnow 0.9.6.rc18 with 4.3.3 firmware. But since your on 4.3.4, ultrasnow will not work even you have updated to 6.15.00 bb. You will just get no service. Ultrasnow needs to be updated to recognize 4.3.4.
But there's another way to unlock it. You have to downgrade it to 4.1. It seems apple is still signing 4.1 firmware, or the hosts file trick may have allowed itunes to confirm/install it. Since mine was on 6.15 baseband, the 4.1 restore ended with 1015 recovery loop. My fix was to jailbreak it with 4.1 to make the system complete the 4.1 restore. The phone got jailbroken, and it successfully downgraded to 4.1 but safari and cydia are not working. So i jailbreak it again with 4.1 with ipad baseband, just to make a clean install.
I hope this would help...i was searching for days and i found someone from another forums suggested downgrading to 4.1.
I'm almost positive you need blobs.
I did not use any shsh blobs. I bought the phone with 4.3.4 bb 5.16.02, and this my first jailbreak with 3gs... i had jailbroken 2 3g phones but that was weeks before i got the 3gs. They were under 4.2.1 firmware with 5.14. bb
I was researching for days and days. I thought i was going to give up on this phone since i cant use it. So now its downgraded to 4.1 and im able to unlock it with ultrasnow. Fully tested with legit AT&T sim and an international roaming sim.
Since i dont have SHSH blobs of previous firmware, i thought downgrade was impossible. But some people in gsm forums mentioned of downgrading to 4.1 so i gave it a try.
thanks... i guess there's not way to unlock 4.3.4 at this time.
i just found out 4.1 firmware is open (doesnt required to be signed.) That's why i was able to install the firmware even without gs.apple in hosts file.