Ok guys let me clear this upfront. I haven’t tested this method yet, but by the looks of it, there is no reason why it shouldn’t work. If you have just got a new iPhone 4 or iPhone 3GS (new bootrom) which is on iOS 4.0.2, you can now downgrade to iOS 4.0.1 without having your SHSH blobs saved. This will of course allow you to jailbreak and unlock your new iPhone with JailbreakMe, and patch it with PDF Patch so that you are safe from PDF vulnerability in iOS 4.0.1.
More: continued here