Hi all, i have an 07 astra 3dr 1.7cdti, I have noticed a noise with what seems to be the terbo in my oppinion. It tends to make a whistling noise generally like in most models but recently has become MUCH louder to the point where it sounds like a police siren!! running ok seems to have lost a bit of power but i dnt really want to get shafted by a garage just yet! any advice to what it might be???