Review on 🔋 Enhanced Fuel Pressure Gauge by Russell Athletic - RUS-650350 by Oscar Kaufman

My 1991 Miata didn't work. I expected this EdleBrock product to work well on my Miata. When the engine is off, it's around 3 psi. When I turn on the engine it drops to 0 even though the engine is idling and running smoothly. Yes, you read it right. In other words, when the engine is off and the key is removed, the fuel pump maintains pressure in the fuel system and the gauge reads 3psi; When I start the engine, the pressure in the fuel system is released and the arrow on the pressure gauge goes out. Next time I will try this sensor on my 1991 4runner. I'll give him the benefit of the doubt. But now I have to buy a special 1/8npt banjo fitting for the gas rail to connect this gauge. If it didn't work on the Miata, I'm pretty sure it won't work on my 4runner or any other car. I'm just confused why it goes from 3psi when the car is off to 0psi when the car is on and idling. Stupidly I threw the box away so I can't exchange it or get my money back.