Sounds like a jet engine shutting down after I shut the automobile off.Sond coming from passenger side. Opened the hood and right behind the passenger side headlamp unit, the supercharger was whining with the engine shut off. I drove the auto 4 miles, from home to work and my top speed was 63 MPH. I didn't gun it. I always baby it. Took it right to MB-Manhattan for serivicing. Mileage is 51K. Still under Star Mark MBUSA warranty, thank the Good Lord. :crybaby2: