shurflo water pump low water flow

You have not told us the type and year of your coach. Many solutions are applicable to specific brands of RV's. For example, this seems to be a pretty common problem with Monaco RV's. The solution, which makes no sense to me but it works, is to put a small accumulator tank right off the water pump. I had tried four different water pumps, even had a surflo engineer look my problem. But, I finally found a service center that recognized the problem right away, installed the accumulator tank, and I have not had any problems since.