Originally Posted by rawdawg
Thanks for the input but I forgot to mention that my rig has the 6.0 diesel. I was hoping that by installing a cat-back I could get a little more HP &MPG. Has anyone done this to the 6.0 ?
What cat back system are you referring to? As I understand this term can imply a straight pipe, high flow muffler, or dual exhaust after the cat. The stock Ford muffler is a bulky, highly chambered unit so replacing it with anything that will free up exhaust flow will help. The most benefit will be gained by also deleting the cat but this of course won't meet legally mandated emissions for some states. As I understand it the main gain is decreased EGTs and turbo backpressure. It may also help with HP gain but from reading various forums not that much.
The real benefit to an exhaust mod for the 6.0, which has already been detuned by Ford to have less HP, is getting away with using an SCT Tuner with a custom program to adjust both PCM and TCM, and also turn off egr flow for less heat and firm up the shifts. Some report a 5 to 10% mileage increase without sacrificing HP by going this route. The belief is also that turning up the hp slightly will help the mileage on the vans. The other paradigm is don't chip the vans because they can't get rid of the heat but these mods will help.
That's pretty much the gist of it from what I've been reading on the diesel forums and from what others have done with their SMBs. I've been researching it but haven't pulled the trigger yet because I want to install a coolant filter first.