HI, I HAVE A LOUD STRANGE NOISE FROM MY CAR. ITS A 2002 E53 4.4I. ITS SOUNDING LIKE A HOOVERCRAFT. WE HAD THE CAR TAKEN APART TO CHANGE THE TIMING CHAIN GUIDES AND WHEN WE PUT IT TOGETHER WE HAVE THIS NIOSE COUPLED WITH A AMBER LIGHT ON DASH (deterioration of exhaust emission control values?)

the only thing i can think of is that we started the car with a pipe off the secondary air pump but fixed this.

does anyone have any ideas? this car is costing me a fortune!!

video of problem http://www.youtube.com/watch?v=uv-mrfOE9V0&feature=youtu.be

it varies with revs and never goes away!