Just a heads up as I went through this and thought others may as well. Look into getting an AFM/DFM Module. They're relatively inexpensive and get rid of the "buffeting/helicopter" droning noise that the 4cyl mode gives you with a flowmaster (or any without the flapper). The linked one is the one I use and only take it out for inspection time since it alters your monitors. Good luck! These trucks sound like a mammoth beast with a nice exhaust/muffler set up!