Yeah, this method would also improve it. Because sbsettings uses the Iphones native built in back grounding without the actual background program. Thus it bogs it down. Ie: if you check your process the phone app will always be running.
Also using an alternate backgrounder will enhance the speed of you phone because rather than it being designed for a 3gs or higher, it is actually built to conform to the 3g'(s) slow processor.
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If you have not already figured it out. To disable the multitasking just ssh into the root of your iphone. Navigate to Simply Adding the following textvalues to the N82AP.plist (which resides in /System/Library/CoreServices/SpringBoard.app/) file will enable Multitasking and Wallpaper on your iPhone 3G:
multitasking
homescreen-wallpaper
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I would not recommend changing the other unix plist's they are built for the iphone 3g where-as the ones I had you replace where set originally built for a 3g'(s) model. Thus by changing these plist's you altered them so that the 3g could more quickly read them.
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I currently am using a t-mobile prepaid plan
