Colin

They removed the catalytic converters totally. I have been driving without them for two weeks now without any problems and the X now feels like a pocket rocket.

We should have a sticky thread for all X5 diesel owners.

hi guys i own a bmw x5 e53 3.0d and i hear terrible whistling sound when i floor it.i think it is the turbo cause i heard it is a common problem with this vehicle.i would like some help on what should i do

They all do that and to some degree, it's normal. If the turbo whistle (or whine) gets much louder, either suddenly or over time, it's likely that the turbo bearings are failing. This will require either a re-build of the turbo unit or a replacement of the turbo. Either repair option should also include replacing the oil lines feeding the turbo bearings.

I can hear the turbo on mine but I have to listen for it, unless I'm in a parking building and have the a window down. :p: