I know this is a long shot but does anyone know what was done to the engine to raise the HP from 18 to 20? The GX355 uses the exact engine as the 355D and got an extra 2 HP....Im looking to get 20HP from my 355D. I know the Rev limit went from 3K to 3600 so maybe that is it? Anyone have any thoughts or ideas for me? The extra RPM / HP would be nice when blowing snow or mulching leaves /wet grass.