I don't believe there's any minimum required gallons per minute for the Shurflo, but having said that I'm also not so sure that I would mess with the stock pump as they are pretty cheap to replace. In fact, I have a extra one if you would like to get your setup back to stock. Pvt. e-mail me if you're interested. I have wondered if throttling the stock pump would in some way harm it, but so far after a year's worth of camping I've had no issues. I suspect now that I've said that it will die next week;)

Troy