I would think there is still something wrong with the fuel. I have very little problems with the LP systems on newer trucks. My one customer that runs 24/7 go 7-10K hours before I ever have to touch LP regulators. These are Yales with Mazda motors (Impco), Cat and Mitsu with Nissan motors (Nikki), and Toyotas (Aisan). They have a Toyota with 20K hours and the regulator has never been touched. Maybe it's because these trucks never cool down and are always at operating temperature.
Yes- thermostat, cooling vents in hood. Everything is identical on both trucks. Can't seem to get any longevity out of Yale's fuel system- gets dirty every 200 hrs- on average.
???thermostat in engine coolant line from regulator???