I have a 09 short bed 5.4 motor. I want to go with a DI/DO single muffler set up. But don't want to loose any torque or mileage by loosing too much back pressure. I don't know weather to go with a
2 1/2 in. from the muffler back or a 3 in from the muffler back out behind the rear tires?

 

dude no power lose thier. only if you run straight pipes then you will lose power. Headers, hi flow cats, and muffler should be fine without no power lose. You will gain power.

 

Your low end may only minorly suffer with 2.5" dual pipes, but nothing too bad. Why do you want a DI/DO muffler if I may ask?

 

I thought as long as I was into it that deep I mine as well go the DI/DO route.
Never saw any body post on the advantages of one over the other.
Opinions are welcome.

 

Hve heard grest results from magnaflow SI/SO sounds great and good power gains .

 

Ifyou are going to run dual pipes I would definitely run an X pipe and two SI/SO mufflers for a better performance experience, and a much better and louder sound. Otherwise keep it SI/DO.

 

^^^ x2