Firstly, XXKPE is a dev release (i.e. unstable). Install XXKPH and see if it works well for you. Read the installation instructions carefully as it involves installing XXKPE first, flashing it twice, and then XXKPH over that (again flashing twice).
I would recommend using CF-ROOT as an all in one solution for rooting, recovery and optimization.
Download an app from the market called "fasterfix". It requires root access and is free. It basically optimizes your ntp file. All you have to do is install it, open it, choose your region, press go, close it, and repeat once more to make sure. It did wonders for me!
As for google navigation, it is disabled for anyone outside the USA. So you must use something like brut.all's google navigation with world nav unlocked. If so, make sure it is up to date (current version 5.10.1).
Hope these suggestions work for you too!
Sent from my GT-I9003 using XDA App