Most people use the boost guage like a vacuum gauge in a gasser, to tell you to lift your right foot a little for better economy. In my truck, I use it to get a baseline on where my truck runs at various speeds and loads, so if there is a problem, I will see the difference and know to start checking for a leak or some other problem. Most guys see the best economy if you keep the boost below 10psi on a stock truck. If you are trying to stuff a ricer, all numbers are out the window, as is economy. I used to leave all stops a little faster than I really needed to, the boost gauge is a good way to let me know to back off a little, if its not needed, and gain a mpg or two.