I just bought a jailbroken 4S, but I want to be able to wipe off any apps/hacks/mods that the previous user may have installed while keeping the 5.1.1 jailbreak intact. Basically, I want only the standard iOS apps and the basic jailbreak software (Cydia and such) to remain in place. What's the best way to do this? Or is there a way to just install the stock iOS 5.1.1 again so I can put a clean jailbreak on it? I want to do this just in case the guy selling it has decided to put any sort of backdoor access on the phone that'll allow him to get back in remotely to snoop on the data.