2004 exhaust extremely loud
 

I've got a buddy with an 04 4500 series with the 6.6 in it and it suddenly got super loud. He's got stacks on it and he said it resonates so bad that it sounds like it's going to break the back window. He also said it sounds the same as a gas engine when it's miss firing. I assume that's injector problems but I'm no expert. What do you guys think?