Just in the past few days Ive noticed a strange noise from my gas cap while the car is idling. It will randomly make a hissing noise then a pop. It doesnt seem to happen in set intervals and the best way to describe the noise is almost like a breathing machine in the hospital. Ive checked the gas cap and it is tight and its been happening no matter what the fuel level is. My mods are AEM CAI v2, invidia header, vibrant exhaust, and flashpro. Any help would be appreciated, thanks.