Harry,
The first and easiest modification to make is to remove the factory inlet water regulator (city water inlet), and replace it with a high flow check valve. You will also have to use a high flow rate (5/8 to 3/4 inch inside diameter) Watts adjustable water regulator (preferable with a pressure gauge) set at 60 PSI at the facet before your water hose.
This modification should increase your water flow rate when filling the tank or using water inside the coach when on city water without the water pump by about 50% or maybe a little more.
There are also other modifications that can be done to improve the fill rate of the tank but they are more complicated and they will give a lower percentage of flow increase.
Gerald