Just installed a 0 - 30 pi westach gauge also. have a wire going from the gauge, to the sending unit, then to the fire wall for ground. Other goes to the fuse panel where pwr is on when the ignition is turned. Have noticed that the gauge bounces all over the place whether the lights are on or off. Highway driving, cruise set, pressure stays around 12 - 14. However, constant stop and go, thing drops to 6 - 10, but will kick up to 12 -14 if i mash the accelerator hard and quick. Sometimes, it will even drop to 0 and stay for a little while, then jump back up to 12 or so. The gauge, sending unit, and the chrome filter cap came from Geno's. I'm thinking that its an electrical problem, the connections, but looking for other suggestions if any before i go doing any continuity checks ( I thought going straight to the firewall wall would be the best ground anyway. Should i go to the engine block itself? Does it when engine is cold or hot too. and what is the normal pressure? life pump was replaced a few months ago along with the injection pump (bad fuel from Cone). 70,000 miles. Thanks again.