If you didn't know Google released a pretty big bit of Android optimization when they released Kit Kat. Kit Kat comes with ART or Android Run Time. The traditional run time has always been dalvik. Dalvik translates the info at the moment you need it to open an app on top of Android. This causes the app to open slightly slower and it is what causes the slightest bit of lag even on spec heavy devices. ART however grabs the info needed to run the app on top of Android is pre compiled once during the install which means your apps should open faster. When tested side by side ART is slightly faster than Dalvik. However the gap should continue to widen since ART is only a work in progress and is very much still beta.
You can now switch back and forth between Dalvik and ART with a simple aroma installer zip thanks to developer "hnkotnis". Simply flash the aroma based zip inside your favorite recovery and you should be able to experience speed and performance on your device. More info on this tool can be found in the link below.
via XDA