So you have an iPhone 4 or iPhone 3GS (New Bootrom), running iOS 4.0.1, with SHSH blobs saved on Cydia, and you want to restore your iPhone again to iOS 4.0.1. Now that Apple has stopped signing iOS 4.0.1, you wont be able to restore your iPhone 4 on iOS 4.0.1 by simply pointing iTunes to iOS 4.0.1 ipsw file. Because if you do so, iTunes will throw an error: “This iPhone [your name] iPhone could not be restored. This device isn't eligible for the requested build.
There is a new video going around in the wild which shows iPhone 3GS (with new bootrom) on iOS 4 jaibroken using an upcoming version of Sn0wbreeze. This video has been confirmed by iH8sn0w - the developer behind popular iPhone jailbreak tools such as sn0wbreeze for iPhone 3.1.3 / 4.0, f0recast and BlackBreeze as legit.
