yep, love the varisteam too.
dont want to sound "funny", but did you disconnect the 2 red wires from the bottom of your pump? i have seen many who have fitted the varistream, but left their wires on the pump which means the pump pressure switch has not been bypassed.
im not trying to suggest you may of done it wrong, just trying to help. its an easy mistake to make.
Gary - WELMAC SYSTEMS