AppSync 4.1 for iOS 4.1 jailbroken firmware is now available in the Cydia. AppSync 4.1 let you install cracked apps on iOS 4.1 firmware by patching MobileInstallation file on iOS 4.1. Once you’ve installed AppSync iOS 4.1 on your iDevice running jailbroken iOS 4.1, you’ll be able to install cracked apps (.ipa) on your iDevice.