max GPM for a stock steering box?

I switched to a Explorer remote reservoir power steering pump and I am having problems with it. So I have picked up a KRC pump which comes with a flow control valve of 2.5 GPM. (That I can cange out for more or less GPM) I now most cars run about 1.5 GPM. There isn't a pressure difference with this pump just volume. I can't think of a reason more volume would hurt but if any smart guys knows fill me in.