After reading over the propane and its burn characteristics I notice no matter what when propane is burned you'll get water as a side effect of burning propane. So the water is you cleaning agent for the carbon build up and such...
Like when I poped a head gasket on the Goldwing the cylinder that got hit with the coolant was nearly spotless...
As for my comment I had to yank your chain a bit there...
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Michael Nelson - 2002 Dodge Cummins