A varistream will fire the pump up for a fraction of a second every now and then just to see if the pressure has dropped, if it has then it will turn the pump on until the pressure builds up again.
You can lower the pressure at which the pump cuts out, this will not lower the flow rate, but it will help with your leaky connections. A bit of experimenting might be in order. It's easily possible on max setting on the varistream that your pump will blow the tightest of connections, as there is now pressure switch to tell it to stop.
Simon.