Hi, all 2018 Cummins deleted with MM3.

Did all the work myself.

I thought the pretty loud whistle/hiss was because it was straight piped, so I bought a muffler.

Still too loud, so I bought a much more restrictive muffler and fired it up last night, and it’s quieter except for the whistling hiss is the same.

Can I smooth this out and quiet it up somehow, maybe with my tune?