When I turn the key on my corolla, there is the sound of decompression of gas

Hey guys, I went to my mechanic and it was actually the ABS pump struggling as the car has some mileage on it, but thanks for the suggestions, all were appreciated

I do not have my foot on the brake when this decompressing sound happens . . I just turn the key, just until the all of the indicator lights light up, then I have the decompressing sound, if I start the engine, it happens shortly thereafter, no matter what, I get that sound, and none of my other toyotas do it . .