Yes you can tell when it kicks in because it gives the pickup a little jerk. If im driving down the road and shut it off and turn it back on i gain 2-3 psi of boost. It really cooled my pyro down, i have the #5 stop plate in my pump slid not quite all the way forward but more than the stock position, without the propane it just to get hot fast (1100 degrees after turbo) and with the propane it hangs at 900 for a long time.
If im running around empty i can get about 2-3 tanks of fuel out of a 20lb bottle. Considering that i only drive 65mph because i never get in a hurry, and i have a u. s. gear overdrive aux. transmission. Then pulling my camper to a different job site, i get about 1 tank of fuel for a tank of propane because it is always using it. When i put it on it didnt kick the propane on till 8psi and i turned the regulator down so it kicks in a 6-7psi.
I just have 2 20lb bottles in my tool box in the back of my pickup box. And the hose run up through the floor and mounted the propane regulator on the inside of the passanger side inner fender.
Kyle