Turbo back can only be done with the cab off. You can only find downpipe back systems for the 6.4L. Just pointing that out to avoid any confusion. If your trying to choose between the SCT and Edge and dont plan on getting any higher horsepower tunes in the future, then go with the Edge. If you plan on going bigger in the future, or even think there is a chance you will, I would get the SCT or Spartan. With the Sspartan, you can get 3 lower tunes for now that are safe, reliable, powerful, and good for fuel economy. And if you want to go big in the future, you have the options of the 250, 275, and soon 310 tune. Always remember that higher horsepower tunes provide the best fuel economy