My son was right when he told me I wouldn't like having a muffler on a powerstroke!
4 inch diamondeye , when I put the muffler on, the turbo whistle is gone. Looke like Imma straight pipe this for sure.
That turbo whistle is too cool to keep quiet!
C

 

i have the same muff on my truck, it took a long time and good few HARD runs and i have half my whistle back! i had a hard enough run were i saw flaming packing coming out of the stacks lmao i was not loosing to that cummins!
its certainly not going to have all that huge whistle back but mine took out that obnoxious bark up top(stacks) but other than that, i kinda like it. when im feeling froggy ill take it back out for the summer