I'm plannin on buyin an 05 and it has a 6 inch stack on it the top of stack sits a little above the cab. Anyhow took it for a test drive and as soon as you get on it you cannot hear yourself think at all. Truck is quad cab and I have 2 boys 3 and 1 and my question is, is that common with these or you think something is messed up with rear window. I've had singles stacks on my old 24v and my old 7.3 neither of those were that bad inside the cab

 

CRs are loud. I had stacks in mine with a muffler and it was still so obnoxious I took them out.