95 GTC odd whistle from dash

[zman99]

1995 GTC Convertible I have an odd whistle which seems to be coming from the dash. It happens when I reach 60 kph and then drops over over 70 kph. Its also somewhat intermittent but more often than not.

It doesn't sound like a belt which in my experience is generally a higher pitched squeal. This sounds more like some air or wind whistling over something and the pitch modulates with speed.

I've removed the plastic liner at the bottom of the windshield and checked the vents and drains and screens etc. All seems fine.

Can't really pinpoint where the sound is coming from from inside the car.

Just wondering if anyone else has/had this problem and if anyone might have a suggestion.

Thanks for reading.

[woodcrafters]

Just taking a wild guess, but it may be a vacuum leak. there are lines that connect to the heater and air conditioner. They are next to the fire wall under the dash.