I have no clue what is making this noise. It sounds just like someone blowing into a tuba horn for about 1/2 second. I removed the air filter and the noise is coming out of the tube leading to the air filter. The noise only happens about 2 seconds after the engine is turned off and only lasts for about 1/2 second. I can start the car and turn it off in 5 seconds and the noise happens. I drive for an hour and thrn it off and the noise happens. The car has 213,000 miles and still runs strong. The noise started about 3 weeks ago. Happens every time the car is turned off. No modification or maintenance has been made in the past 2 months. Any thoughts would be appreicated. Thanks