Maybe I was not clear so lets try again. They show pressure fine. However they are VERY slow to react to small changes in pressure. In other words if oyu have a problem it MAY not ever show on the gauge. We thought we had a few pressure issue, chased our tales trying to find something elseas the gauge said all was well. Remove the isolater and viola we have a fuel pressure issue, I have seen it three other times. IMO they are fine for a street car but have no lace in a race car. If you want one PM me I will make you a smoking deal on one.