Car is a 2017 WRX Limited, all stock. There is a weird buzzing or vibrating noise corresponding with engine speed coming from the engine bay. It only happens under deceleration above about 3800 RPM and sometimes has a phase shifting quality to it. Car runs and drives fine otherwise and shows no other signs of abnormality. Its done this since I began going over 4000 RPM after the break-in, since I've had it. See video for example. You may have to turn your speakers up and ignore me yakking about it...