I've discovered in the last 4 years that automotive fuel pressure/ vaccum test gauges are TERRIBLE for accuracy. I've tested maybe 4 different once and they are horridly inaccurate.
These were compared to "suspected good" better quality vacuum gauge that had in turn been compared to micron vacuum gauges and digital manometer
(I had planned to build a good old fashioned glass tube mercury barometer, but in this communist country I could find no way to get mercury)
