http://en.wikipedia.org/wiki/IPhone_OS_version_history#3.1 andi thought blacksnow did not unlock 3.1?
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So in order for me to unlock my 3gs 3.1 Firmware 0.5.11.07
I do the following
1. run blackra1n
2. run blacksnow
3. insert sim and talk away?
Is that it?
http://en.wikipedia.org/wiki/IPhone_OS_version_history#3.1.2
They both have the same baseband version in those firmware versions.
As for your steps you are close:
1. run blackra1n
2. run blacksnow
3. ???
4. Profit and insert sim and talk away?