To DG_F150
I installed the Flowmaster 17226 Cat Back on my 02 Screw FX4 5.4. SS tips exit behind the wheels on an angle almost at the rear corner of the bed. There was plenty of room to move the pipes around the spare. Sound with the 50 series the comes in the kit is mild inside and out but you know it's there when you stomp on it.

 

I just put on the Magnaflow kit #15749. I absolutely love it. The kit is made exceptionaly well.
My truck now has a nice grumble. On acceleration its noticeable. when you get to crusing speeds it quiets out. Hardly noticable.
I would recommend anybody to buy this kit.

 

I had the local muffler shop install the 5X11X22" #14588 stainless Magnaflow muffler with a single 3" inlet & dual 2.5" outlets. They used 8ga. pipe and took their time doing it.

The truck runs a lot better and the mileage improved. It is quiet but you can still hear it.

 

Oddly enough....

I just had 12579 (5x11 SI/SO) installed onl my my '03 S'Crew today. Nice and quiet still, yet has a lower V8 growel to it, and no droning at speed. Throttle response is DEFINITELY better, and its picked up a couple HP for sure. Cant wait to see if it helps the MPG.

 

I love my magnaflow system, it has a nice growl to it, and I increased my mpg

 

Responding to some posts earlier in this thread it seems to me you could manage to get a Dremel or something small with a small cutting disc into the inner pipe and zip 2" or so right out of there.

 

That might work. This tubing is pretty tuff, I know a hacksaw won't cut it. I modified mine to exit on an angle and eliminated the inside pipe from showing. My tip browned after using it but cleaned it with soapy water and a scotch brite pad, now it doesn't brown or seem to as fast.