Certainly sounds like an air leak, if the turbo is working properly and the power is OK it will be on the inlet side, the pipe that goes from the air filter to the turbo, often the pipe comes partly disconnected from the turbo.

hi flowerloverman

In my experience the leak is more likely on the output side of the turbo my reasons for saying this are twofold 1 because by your description the noise only really starts from 2000rpm ie when the turbo begins to push and 2 because I've come accross it several times before on various vehicles both lorries and cars TIP : first make sure all the hose clips are seated properly and are secure if they are you probably have a split rubber hose which can be almost invisible if you dont know where it is .But if any of the hoses are very oily that is a giveaway look at those first especially if theyre very soft

Hi just thought i`d say thanks for all the advice, the car is now back to its old self with more power on top , the problem turned out to be the intercooler it had a massive hole on the back of it and it was letting all the air out , the mechanic i took it to 2 weeks ago has really ripped me off for the last time, so all in all 10 pounds for a second hand 306 intercooler and 20 pound to fit it , i think thats quite good , thanks again simon