is it real? Downgrade iOS 4.0.2 to iOS 4.0.1 without SHSH Blobs
just found it! . haven't tried it. Anyone know how legit with this link
How to Downgrade iPhone 3GS iOS 4.0.2 to iOS 4.0.1 without SHSH Blobs
Step 1: Download 4.0.1 ipsw
Step 2: Extract it with winrar or winzip to a folder on the desktop. You may need to rename the firmware file from .ipsw to .zip to do this.
Step 3: Open the buildmanifest.plist with the notepad. Search and replace all – 8A306 with 8A400. Save. Repeat the same with the file restore.plist
Step 4: Download 4.0.2 ipsw and open this with winrar or winzip.
Step 5: Take all the files from the 4.0.1 and drag them over to the 4.0.2 zip archive that you have open.
Step 6: Delete all the dmg files that have 002 at the end, leaving only the 001 files left.
Step 7: Save the archive. And rename it back to .ipsw if you changed the name to get winrar/winzip to open it.
Step 8: Optional: (this helps ensure you get an SHSH file request for the future, but should not be necessary to just restore 4.0.1). Add the 220.127.116.11 gs.apple.com line to the host file (you may follow our previous post on how to do this).
Step 9: Put the device into DFU mode, open iTunes and restore the firmware you changed. Wait for a while and it will restore your iPhone to iOS 4.0.1
Note: this only works due to the similarities in 4.0.2 to 4.0.1 and 4.0. This will not be a way to downgrade to 3.1.x and may not work in future firmware updates.
Voila! The downgrade from iOS 4.0.2 to iPhone iOS 4.0.1 is successfully completed. You can now jailbreak your iPhone 3GS with jailbreakMe and carrier unlock with ultrasn0w easily