I have used Firestone bags on my last 2 GM Duramax TV's. I'd air them up to a given pressure, usually about 50 - 60 psi, IIRC, then hook up and drive to a flat area and look at the level of the TV and 5er. If necessary I'd release a little pressure to get level. It seems as if the pressure went up with the weight added. I'll have to pay attention next time I hook up. I don't have an attached gauge and don't see the need for one on my TV. Once I have the correct air pressure to level the TV that's where it stays.