I have a 2003 Z71 with a 5.3 in it, to me it seems like it doesn't get it like i think it should. In comparison to my dad's '99 mine feels like a dog. From a stand still you kick it down and it will **** and get pretty good, but from anything above that I will kick it down and it doesn't seem to downshift like it should. Any suggestions?

 

Just guessing here, and if both are stock. The 99 has a throttle cable so when you floor it opens all the way. The 03 has drive by wire and the PCM will rarely open it all the way, just to name one.
You need a tune. I use Nelsonperfromance.com. I never used anyone else but from my experience I will not look elsewhere. I had a hand held and considered it a waste.
Do a search on "Torque management and Nelson Tune".

 

How Many Mile On The 03 Their Are A Few Things That Could Be Wrong

 

The '03 has 57,000 miles on it. I have used the Hypertech power programmer and installed a K&N FIPK, other than that just stock.