4inch downpipe
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I ran a stock exhaust with a cat/muffler delete for a while. It's a raspy sun of a gun! It's probably one of the louder exhaust setups I've run believe it or not. I think a 4" turbo back is about as loud, but deeper. 5" screams inside of tunnels and garages kind of thing, but not noticeably louder than the 4", and my stack setup is LOUD inside the cab, but outside is a little deeper and not as loud as a turbo back setup.