actually the 5" straight pipe on the 7.3 is about the same decibel level (or close to) the 4" system. but I've noticed that the tone is deeper and i hear the turbo whistle much more. you hear the waste gate open quite loudly, which i like a lot. It wont be as loud as a 6.0 straight pipe, but i think it's somewhat close, just not as high pitched. And i'm talking about 04+ 6.0's. the early 03's (with the silencer removed) are the loudest sounding turbos i've heard.how does it sound i wont to do a muffler delete on mine to make it louder .. is it louder than the four you had ?