i have a 5.0 and my friend has a 4.6, we basically have the same exhaust we both still have cats and a y pipe to duel outlets the only difference is that i shrunk it down to 2 inch pipe out the back and he has 2.5 his is louder than mine i couldnt beleive how much louder it accually is, i was told by a pedestrian that mine has somewhat of a nicer tone
why r these newer engines so much louder

 

The old cats were a lot more restrictive than new ones. The 2.5 inch pipe makes his truck louder as well, but take solace in the fact that he's also lost all his low end because of it.