i have an iphone 3G jailbroken 3.1.2 modem firmware 05.11.07, i want to install the same firmware again to refresh the phones wifi is not working some times. i want to use blackra1n ... how can i keep all my existing apps as the iTunes account is now different from the one apps had been purchase. ( i have bought the phone from some guy who has bough many apps with his account).