I had the dual out flowmaster on mine... 50 series. someone recommended this for the CTD and if I'd seen this when I had my gasser, I'd probably tried it. the guy who installed it on his ram (diesel) said it brought back alot of low end torque that was lost when he went to an open exhaust. mine sitting in the garage waiting for another week or so (valve body going in Fri or Sat).

http://www.aeroexhaust.com/