Dyno tests seem to show the rubber accordion style hose between the air box and TB to be the biggest problem as it causes turbulence.
Mine is only a 5.3L but I am running a K&N drop in filter and the Airaid MIT which smooths out the flow.
I also opened up the fender opening behind the air box. It may not be needed but it certainly can't hurt.
Here is a before shot of the air box.
And an after.
And the inner fender, showing where to cut.
Some people prefer a dry filter over the K&N which requires oil. Either one is good as long as you don't over oil the K&N as it can cause problems with your MAF sensor.
Factory air box is best IMO because it is already a "cold air intake" because it pulls air from the wheel well rather than the hot air you get with a open element/cone style filter under the hood.