Gonna wake up a moldie oldie
I have excessive engine noise from my 5.9 as well.
I have an 03 3500 that has recently gotten loud. It's just a standard loud engine noise. It starts to get out of control around 1600 RPM and up. Of course, Cruising speed. It literally drowns out the radio at 70
The mods are turbo upgrade from a stock 341 to a stock 351, BD intercooler, and a Pusher air horn. There's more, but that's what would matter. The truck is pushing 25 MPG. I checked for leaks, loose bolts, everything. It seems to be louder on the left than the right side.
It's not a whoosh, a tic. It's like you were sitting under the hood. I installed a hood pad from Dynamat too. It's just a loud fast running diesel noise. All other systems are OK. I thought maybe I used the wrong weight oil, and changed it. It only helped a little.
Any ideas?
Darn thing really needs another gear