maybe it's the heatsheild thing - but when I start from cold, there's a whistling noise coming from the rear of the car, kind of like what you get when you blow across the top of a bottle. After a few minutes it disappeards, and only seems to be at low revs

any ideas? cheers

iv got that, 4 me its just the fse boost valve.

On the FSE it's a case that its building up pressure.

As it's coming from the rear it may be the fuel pump doing the same.
The fuel pump is located directly under the rear seat - is this where the sound may be coming from?