because I'd open the gas cap and sometimes major fuel pressure is released. Last summer on a hot day after I shut the car off I heard a long sound it sounded like "eeeeeeeeeeeeeeeeeeeeeee" and I was like wtf is that noise, I'm looking under the car, tires and I was like its gotta be something fuel pressure related, I open the gas cap and major fuel pressure is let out and it goes away. But sometimes I still hear/noises from the fuel tank/fuel pump and I think thats whats causing my alarm to go off a few minutes after engine is shut off. It only happens for like a good 30 seconds or something then it goes away fine. But that vibration is causing to set of my alarm when I arm it right away and walk away from the car.