I had the Mufflex/Magnaflow 14, but then put the Flowmaster Super 40 on after the Mufflex kept coming loose and leaking on me. The Magnaflow was nice, but the Flowmaster is a little better. The Flowmaster is louder at idle and acceleration, but a tad quieter at highway speeds (unless you floor it).

I also have the resinators removed, which killed a lot of the highway drone.

 

I also installed the Super 40.. Sounds great and i have never heard any drone sound..

 

just got mine in the mail the other day -- now if my frikin 2010 Power Wagon would show up in time lol -- should be here tomorrow -- ill post pics -- and some video when i get the muffler on