Fiesta Tdci '04 - Hissing/air Noise In Higher Rev's

[tired_boy]

If i dont push the car at all then you won't hear anything but when i accelerate hard in 2nd 3rd or 4th (i havent tried 1st and prob cant go fast enough in 5th) i hear a hissing noise that gets progressively louder (but not particularly loud) as the revs go up. It take a while to show iteself, again i can drive around quite steadily and never hear it. As soon as i come off the power it stops. It almost sounds like air hitting the car at a funny angle on a blowy day.

Any ideas?

[tired_boy]

Anyone? Not that hard for the experts surely?

[mintalkin]

have you checked all the rubber vacume hoses for splits or leaks,also check around the injectors for signs of diesel as its common for the injector seals to wear.