my recently purchased x5 was very sluggish after finding the fault (a vacuum pipe slit) 

since the repair the car now has all the power back but at about 2000 rpm there is a 

whistling noise and at 2500 rpm its a screaming noise . i have checked all the turbo 

pipes and inter-cooler. it only happens while under load when i rev it parked to about 

3000 rpm you hear the turbo as if there was a broken pipe on deceleration (a wooosh noise)

any ideas? any help would be gratefully appreciated.

 

It definitely sounds like turbo boost pressure leaking from one of the hoses or intercooler....you would have to have someone on the throttle holding it to boost pressure while you listen to where its coming from.

 

i have taken your advise and had someone on the gas while it was on the ramp and from the underside listening to all around the intercooler

and pipes it seems to be fine and the noise is much quieter from there.

but when i lowered the ramp and listened from under the bonnet the noise is very loud

i have taken the air filter out and replaced it but the noise remains the same???? 

its to loud to pin point it. 

Morning Terrence

Not a diesel driver but I have owned (and still own) super charged and turbo charged petrol cars so my thoughts would be.

Turbo's do wear and whistle as a result, a whoosh on Deceleration could be a waste-gate blow off stopping over boost on the overrun. I thought most these days bypassed any over boost into the exhaust to silence the Whoosh so check the plumbing again. The whistle rising to a screech doesn't sound right to me I would suspect a worn turbo I am afraid.

Dave