I'm in the process of determining what approach to take with putting a new cat back exhaust on my 03 F250 SD 5.4. It has a K&N cold air intake on it and that about sums it up. I'm looking to get some added torque while towing and a decent sound (not something too loud on long trips). Better MPG would be nice on the highway too (getting about 13.5 to 14.5 now).
My thoughts are a Magnaflow or Borla behind the CAT and either exit infront of the rear wheel or in the stock location.
What is my best bet? Pros and Cons to exiting in front of the rear wheel?
Pros: pipe dont rust out as fast
annoy stupid drivers on the passenger side
sounds better IMO
Cons: passengers complain of exhaust noise, driver dont hear it so much
I am quite fond of my gibson exhaust. Based on my research the best thing you can do is eliminate the goofy y pipe.
I still have stock y pipe, no cat and the gibson supertruck exhaust and i noticed it helped the mileage a bit. With my 3.73's, 33's, and a light foot I've been getting about 500-550 miles per tank expressway with some city.
The stock exhaust is 3" so you might be better off just changing the muffler I went with a flowmaster 50 series which is just a little louder than stock. I also went with a SPD ypipe which is a must do if you are doing any exhaust work that made the truck sound and feel better.
Exiting in front of the rear wheel can get droney and annoying on long trips unless you use a very large muffler. I used to have a lightning style exhaust on my truck so I found out all about it. MPG or performance increase from a catback is little to nothing. I experienced nothing.
A single 3" catback exiting in the stock location is what I would recommend. If your stock exhaust is in good shape yet you can just replace the stock muffler and add a shiny tip to the tailpipe. The Flowmaster 50 SUV muffler will give you more sound but not be overly aggressive. I would recommend replacing the stock y-pipe (where it necks down) with an SPD unit. The stock y-pipe necks down to 1.5" from 2.5" at two places and hurts power. A good custom tune from a place like 5-Star would help give your truck more performance and get the A/F ratio back in line which was thrown off by the intake.