I have an apexi AVR-R boost controller. It works fine. However the last couple of months when I shutoff my car, the solenoid under the hood makes a sort of rattling sound. Kind of like that plastic wheel from the game of life or a cheap roulette wheel. It even vibrates to the touch. This lasts for about 5 seconds. It never happens when the car is on and does not affect drivability or boost control. I had an extra solenoid and changed it out but its still happening. Does anyone have any ideas or have the same problem with this boost controller?

 

All i hear is a slight buzzing type noise for a few seconds and then it turns off.

 

Yes I get that same exact noise. Is that normal?