I have a 2003 F250, 6.8L V10, 6 speed Standard.
I wanted to put an aftermarket muffler on it to make it sound good and maybe gain some extra ponies and a little bit of gas mileage.

Now, Ive heard putting pipes on a V10 will make it sound like a 6 cylinder

So, I decided to experiment. The V10 has two, 2 3/4" pipes running off the headers into a Y 3" pipe. That connects to the Catalytic Converter which runs into the muffler and out the back of the truck. The muffler on the truck was attached by a bolt on strap. I undid the strap and worked the muffler off. I left the Catalytic Converter in place. Keep in mind, this is a factory set up.

I was about to put the Flowmaster on, when I thought, what the hell. I got in and started it up, just to see how it would sound. Too my surprise, it actually sounded good with no muffler!! Even after I revved it, the pipes didnt ping like I thought they would!!

IMO, it wounds like a Corvette exhaust system; A low, steady rumble when idling that drops off when you put it in gear. It has a lower sound than a Diesel truck, and we all know how noisy those are!

So I left the muffler off, removed it all, and kicked the tail pipe out the side, in front of my rear wheels. I think it sounds good, and have noticed an increase in power. I am hoping it will get me better gas mileage (im running a steady 15 mpg Hwy).

 

The only thing you might want to worry about is that I've heard dumping the exhaust out the side before the rear tire could potentially warp your wheel. I love the sound of a truck with no muffler... Don't have one on mine No CAT either.

 

Hmm. Iv never heard of that, though, that makes sense. The outlet is a good 2ft in front of my back tire. Its just behind the back door (its an extended cab), so maybe that is far enough to keep it from doing any harm.