I just wanted to know do you gain anything by gutting out catback on a 5.3?
And also what exhust would be better for me if I want max HP but don't realy want the loud noise inside the cab. What I mean by the loud noise is I don't like that at 2000 rpm with a flowmaster II its huming inside the cab I would only like it when you get on it, the noise.

 

Well if you mean gutting as in just going with straight pipe after the Cats, I can tell you I did this with my 99' and it sounded very loud and mean as hell.
I loved the way it sounded but it was just too much for the area I drive it and the low speed 1600-2000rpm range was just too much inside the cab.

Magnaflow offers some really good mufflers that have low interior resonance, produce HP, and sound good too.

I love my Corsa Touring, no drone what so ever and it sounds great at WOT. Maybe a little too quiet during everyday driving but at least theres no drone. Pricey but well worth it.