In my experience and driving nearly 1,500-2,000 miles per week, there are two major variables that are difficult to obtain what everyone on here is doing. The first is RPM. If you can keep your truck below 2,000 rpm's your mileage will be substantially better. Many people might run 70 mph @ 1,900 rpm's on the hwy and get 19-20 mpg with the Spartan. I know my truck can do this. However, I drive a turnpike everyday that is nonstop and a speedlimit of 75 mph. I drive 78-80 @ 2050-2150 rpms and my mileage is 16.8-17.5 hand calculated. I am running the 210 tune right now and plan to move to the 275 soon.
The second major variable to consider is how much fuel is actually going in the truck. It is best to spend the 5-10 extra minutes to fill the tank all the way until all of the foam actually dissipates from the tank and you can see the fuel in the neck of the tank. By doing so, you are able to ensure that you put the same amount of fuel back in the tank each time and obtain the most accurate hand counted mileage. My guess is not everyone practices this when claiming mileage gains.
I tried nearly every tuner/programmer out there with/without the delete pipe. There is no comparison to the Spartan from power to economy gains to customer service. The Spartan also is 100% consistent with every tank I put in my truck. You definitely went the BEST way with Spartan!