my friend has NO mufflers on his (truck 5.4L V

and its LOUD!! and 3 cops in one day asked where he got it done and they said it sounded great... i go my stock muffler cut off and put a muffler in the read and it sounds great.. and noone said anything about that
I think its 5.4L not 4.8 sorry he has a 2007 Chevy Sil. Truck. Single Cab Long bed. Its Blue