I've had one on one of my cars, daily driver, for 10 years now.
Autometers first generation isolator sucked and had diaphragm problems.
They sent me the newest one for free when I told them about how it failed.
The second was extremely accurate for about 8 years.
Now I think there's an air bubble in the line so it's off a few pounds at idle, no biggy.
You can't set the static fuel pressure when the gauge can't be seen in the car, when you're adjusting the regulator anyway, so I add my portable one to do that task.
As long as it goes up 25psi. or so when I go WOT I know all is good.
50/50 anti-freeze and water goes in the line inside the car, I've got a -4AN braided line inside the car but I think I will be replacing that with 1/8" plastic line which should be easier to bleed in my application.
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