In my 2003 Copen, when I put my foot down and the turbo kicks in, there is a loud whistling or shrieking noise. Does anyone know anything of this? I let a friend's husband, who is a car mechanic, take it for a spin, and he says the car is running just fine, and he doesn't know what the noise is, but he doesn't think it should be there. As this is the first Copen I've ever seen, much less driven, I have nothing to compare it to. But it is kinda embarrassing. People tend to stare at Copens anyway, but a lot moreso when it's screaming like a banshee. The only thing the mechanic could point to was the round aftermarket air filter that someone has fitted. "Maybe it's coming from that", he said.