Now we also installed my dad's turbo back(single set up) on his 99 Cummins. I thought this would sound nice since the muffler was around 30 inches long. He fired it up and has a loudness at idle, but when on the highway you can't hear the exaust over the truck. Even when taken up around 2500 RMP it sounds nothing like the newer gens. It's odd how I have a def. exaust roar, where on his you can hear the engine really roar, so I guess it's two different sounds. I guess the motor/turbo design is what causes this? (I'm fairly new to diesels so I'm not sure) Overal a thumbs up to MBRP systems, they perform as they claim and sound great. Now only if I had somebody that could stand outside the trucks and take a sound clip of them. I'm working on that next though.