Installed high pressure regulator at connection below deck. Tried starting unit and it ran, but sounded rough. Turned unit off and installed a tee to check gas pressure. We had 11 inches of water column but unit was still not running properly. Called manufacturer to see what the BTU requirements are to see if maybe the unit is starving for gas. They were unable to provide btu rating for propane. Asked them why the unit isn’t running smoothly when we have the required water column, after a 30min hold they mentioned we are supposed to remove the high pressure regulator that came with the unit and still use the low pressure regulator. I disconnected the high regulator and just connected the low regulator to our gas line and the unit worked as should. Ran quiet and smooth. Reconnected the 2 regulators back up and left them as I found them. Not able to contact homeowner at this time since he is at work and unable to receive calls. Technician wasn’t sure if homeowner was ok with disconnectin