Not sure if this has been asked, but I didn't find it anywhere... I warm up my car in the morning and let it sit for a bit before I drive away, but after the initial warm up (You can tell when the rev drops back below 1k that it's done), I can sometimes hear a high pitch noise thats very subtle from within the car. However, the moment I walk towards the engine bay and open it up, the sound disappears. If I give gas to rev up the engine, it'll also disappear, but as soon as the rev returns to idle ~800rpm, the sound appears again. Anyone know what issue that is? Thanks!