This guide is only for iPhone 3G users with iOS4. Its well known that iOS4 slows down the iPhone 3G a lot and almost makes the phone useless. To remedy the sluggish performance (or at least one cause of it) go to “Settings – General – Home Button – Spotlight Search – deselect every option” and this will stop background indexing on the phone. Several users reported that the fix showed immediate results on the iPhone 3G. Its worth a try!