I'm on the same boat. I get 11-13 on my normal driving which is 99% city, but when I take it in the highway I've seen 21 hand calculated.

 

I Wish I Could Do That

 

i have 500 miles on my 06 CTD and my first tank i easily got 18mpg. i guess it is all how you drive, most of my miles are highway at 60-70mph...

 

I get aroud 20mpg on mine with the mods and the box turned off thats mixed driving and running Royal Purple, turn that box on it drops to 17 -18

 

Sounds to me like you are a little off on the MPG chase... I drove thru Kansas City traffic and up and down 71 Hwy at 75 mph for a few months and would average 15. I'm back home now and on open roads under 60 mph, I'd avg 17... Add the Juice/Attitude and K&N and now I'll avg 19 if I keep my foot out of it.

If I'm pulling a trailer, cut all those numbers in half.

 

Just bought my first bottle of Howe's meaner kleaner and I'm seing 14.5 Mpg on the first tank of use. (mixed driving) Not a significant improvement but hey anything helps.

 

I've been getting 15-16 city, 20+ hwy with #2 diesel, but now that winter's here my mileage has dropped to 13 city, 17 hwy. Sucks.

Well, I have 10,000 miles on the clock now, hopefully everything will get a little better in another 10,000.

 

Anyone that would tell you this is UNINFORMED!! I have had muffler shop guys tell me this as well. The truth is that this is a BOOSTED motor. Unlike a naturally-asperated motor that does rely on cylinder scavaging to produce torque and HP. As long as the turbo can breath properly, BIG in and BIG out, it will make power. The length of the pipe in front of the rear wheel to the back bumper would not make any difference. Anything you can do to help the turbo breath; cat-delete, muffler-delete, or straight-through type mufflers. Again, the key word here is BOOSTED. That thing under the hood that is singing to you is your friend.

 

That is exactly what I told the muffler guy, but he has a CTD as well as 5 of his buddy and said a couple of'em did what I wanted to do and lost out. I guess my question should 've been if they did anything to the intake to match the new free flowing exhaust.

By the way general I've got the the 03 Ltz 400 as well
White Bros. E2 exhaust W/ head pipe
K&N Intake
Jetted
Renthal bars
Sand Sharks (never mounted)
This quads is great and has served it's purpose very well for me, but, I want the new Raptor 700.