So, I was trying to decide Magnaflow or Flowmaster or Imco or blah blah blah....I researched a bunch of them. Then I went down to a local muffler shop in Anchorage, where I live, and talked to them about my 2005 5.4 3 valve FX4. I ended up getting 3" pipes from each cat back to 24" long, 3" in diameter vortex mufflers which leave into a X pipe and continue as 3" out the back into 4" stainless polished tips. OMG. $675 and worth every penny. I didn't want loud, just deep and throaty. I got exactly what I was looking for.

I lost a slight bit of low end right at take off, but with my Air Force One intake and 3" true duals w/X, at about 2500-3500 rpms, it rocks hard. I smoked a 5.7 Hemi with no problems. It was slightly ahead off the line, but when I hit 2500 and climbing it was over. Sounds great, better performance, but mileage is only slightly better (.5 mpg) on the highway or worse in town (cause I can't keep my foot out of it).

Xcal 2 ordered. Should be here in 3 weeks. Oh yeah.

 

I don't know what your exhuast route is like, but if it's like my 95, they are probably only worth 2.5" due to compression bending. That's still plenty though.

 

excellent choice man, the local muffler shop usually can do so much better than a bolt on cat back system man as you very well know. Its usually cheaper too as cat back run around 4 or 5 hundred is suspect yours was a little bit pricier as it is dual and more materials and work, nice man i bet its great.

 

2.5" is a big of pipe u would want for a 5.4L any bigger and your loosing exhaust velocity

 

3 in. pipe that's pretty large.