I'm a flowmaster diehard... The muffler will definitely make your truck "louder". But the big echo is from the pipes, that is what makes the truck really loud and gives it that deeper sound. So, if you don't want an echo then don't put big pipes and tips on your truck after you do the muffler.
Like my truck, I put a flowmaster muffler on my truck. Then I put 18" x 3.5" in. tips on my dual pipes and the noise was substantially loud and meaner.... And I also have a 5.4L.
Hope that helps.
Last edited by Regulator; 07-08-2014 at 07:40 PM.