Hi Uplink1001,
There are many factors that can effect the performance of your app. Let’s start with iphone4 this device is near end of life as apple will very likely obsolece it with next major update such that you can no longer install apps on it, e.g., ipad1 was obsoleced and can not be updated to ios7.
If you are using lists and they are very long lists you should consider minimizing the length of such lists and definitely minimize the graphics you use on the page such as gradients or large background images. A quick insight into what happens when you scroll such graphical lists the device does a lot of buffering that is computational and memory intensive.
Lastly you should consider dynamcially loading screens into the DOM to also management memory. See this thread: http://www.genuitec.com/support-genuitec/viewtopic.php?p=19498#p19498