My Vec has recently dveloped a whistle when it is driven above 30mph. The only way to describe it is it sounds like when you blow across the top of an empty bottle and you get that hollow whistling sound.

I have checked the air inlet tube to the air box and filter and it was a bit lose. I put it all back together tightly and it has improved slightly.

I have been underneath the car and made sure the 'belly pan' is properly secured and had a good look round the engine but it all appears to be fine.

The performance and MPG have not altered but for the life in me I can't work out what is making this noise. It is obviously speed/wind related but it's driving me mad.

Anyone else had a similar problem or any ideas where else to check?