The Flowmaster 40 series is awesome for the first little while, but the drone at highway speeds will make you want to kick a kitten across the street. Too boy-racerish and you won't be fooling anybody into thinking that you possess any real power under the hood with your tractor straight 6. I hope it's at least a 6 because a high flowing exhaust on a 4 popper sounds like a weedwacker IMO.
A quality Gibson or Magnaflow has a mellow hum that I lean towards.