Can you be more specific as to what you're asking? I'm guessing you're comparing native performance to PhoneGap performance, but I'm not sure, and to some degree, that's a flawed comparison anyway (it's possible to create slow native apps as well as fast PhoneGap apps -- it depends on how they are written).
In order to provide better answers, you're going to need to provide some context, example code that demonstrates the problem, Versions of plugins & platforms you are using, OS version(s) of device(s) you're testing on, and profiling information (you should be able to get this from chrome://inspect).
It's also worth checking out Jank Free: Let's Make the Web Silky Smooth! which has lots of useful information.