I am posting this because I have been searching for this a couple of hours and no luck. i have a working unlocked 3gs filmware 5 11 07 that had couldnt find the network even though it read the sim card. i had to to restore because it kept on freezing on me. so i used pawntool for a mac to make a custom filmware and i restore using itunes and custom filmware. i then downloaded ultrasnow 0.9.3 using repo666.ultrasn0w.com. and finally added blackra1n.com to my sources and blacksn0w.com (to tell you the truth both said it couldnt be added but when i clicked on the source "entered by user" it said install and it did.) and vola it worked.
ps my APN is internet2.voicestream.com
and my mms APN is wap.voicestream.com

SO HAPPY!!!! long live T-Mobile