Yes, it's there for when you start to load up, helps keep it closer to or at level as well as better overall vehicle control. I had a setup on my 08, I used it mainly for towing, put a flatbed trailer and a car on the back it would squat pretty bad, nowhere near capacity, just soft rear suspension and with a u haul trailer, don't have much option for moving the load around to curb that. Somewhere in the cab, you should have a gauge and switches for increasing and decreasing pressure. Looks like a firestone airbag, Just have to look around, some mount the gear in the center console, others at the bottom of the dash. And to our Member Down Under, again, lots of us run or have run them, usually set them to at a minimum of 5psi when not loaded down (recommended by manufacturer) And then when you hook the trailer and load it, air them up to level, I think when I would tow it was roughly 40psi I had to bump them to. My sig has the link to my install.
