From the serial number, my iPhone 3GS was made in Week 39 of 2009, which I think puts it in the gray area of old vs. new bootrom. However, I bought it already jailbroken/unlocked, and I am able to turn it off and back on without being tethered. Does this mean I'm on the old bootrom? I'm looking to upgrade to iOS 4.0 with the new PwnageTool 4.01. Also, will it remain unlocked as well as JB with the new Dev Team tools?