904 in the Demon, Tranzact brake. Completely rebuilt at the beginning of the season

Seems lately having a harder time to get the brake to hold without running up the RPM some at the line. Once locked it holds fine. Also notice I need a little more RPM to get it into reverse. Been told the pump could be weak. Tried checking the line pressure with a gauge, and getting no movement at all. Obviously has some sort of pressure since it's still functional. Any ideas where else to look?