This is the reason that both my Dad and I bought Smarty Jr's. We both only run on SW1, which is timing only... no additional fuel, so your not running the LP, injectors, CP3 any more than you are stock.. but you get a hp gain from the timing. That also means the hp is "free". The hp/tq gain on SW1 is where you want/need it.. in the 1800-2200rpm band it makes about 55hp more on TM4, but at peak rpm, 2900, its w/in 1 or 2 hp of stock. So what that really does is makes the truck a 325/700 motor... which is great when towing.

This is the same reason you can see a mpg gain... your making more hp per drop of fuel burned, so it takes less fuel to make "x" hp.. The gain in efficiency is smaller at the hp demand is lower.. i.e. empty cruising, but as the demand increases, towing, the efficiency in noticed... But one caveat to that, if you drove your pyro with stock programing you will see a MPG decrease, as now you don't run as hot and can drive the road, not the pyro, so your going faster than you were before... But if you just towed in cruise control before and will drive the exact same afterwords then you will see the largest gain... How much is very driver/rig dependent, but the physics is there..