Sorry new here
I have a stock 03 with the 4.8 and i just put a hooker muffler on and its still way to quit. If i take the cats off will it get louder and sound good ? Also where do i get o2 sims at if i do take the cats off ?

 

You will definately notice it to be louder, but most of the time removing the cats makes it raspier. Also look into longtubes to make it louder. O2 sims can be found at most any performance store. Check out www.thunderracing.com or www.tbyrne.com They are sponsors here.