Apple’s iOS Simulator is great- I use it all the time because it is so much easier than running on a real device. It has a few drawbacks, though, one of which being it is too, well, powerful. Because it has access to the computer’s resources, I often find that code that runs well (smoothly) on the iOS Simulator does not always run smoothly on a real device, in this case, my iPhone 4.
The title of this question says it all, but I’ll say it again: Is it possible to make the iOS Simulator perform like a real iOS device?
You could use the ‘nice’ or ‘renice’ commands to change the lower the scheduling priority of the simulator, but it probably won’t help much unless the are some other, higher priority tasks running at the same time.
Personally, I think you’d be better off spending your time getting the hang of running on the device. It’s really not that difficult, and you’ll end up with a much better idea of your app’s true performance.