Whistling sound?

[dazmul1]

Hi I’ve had my car around 6 weeks now and all has been fine (2009 x5 35sd), had it serviced after I bought it and health check at the same time, just lately it seems to be whistling from start up, noticeable on tick over and when accelerating, I’ve no warning lights or codes when I use bimmercode and car drives absolutely fine, should I be worried about the turbo’s?
I checked pulleys and belts they are all okay so I’m thinking it’s a turbo noise I just don’t know if it’s normal or a sign of impending doom.

[X5Sport]

Does it only do it when cold? My 40d starting doing it after a service a year ago and I have no idea why. I can only surmise something isn’t back quite the way it was. It definitely increases in pitch with throttle but isn’t the really high pitch from a turbo. Still trying to work it out. It disappears as soon as the car warms up.

My thoughts are around some soundproofing, or the air filter. All the hoses are in place and the turbos seem to be doing their thing. No excess oil consumption or signs of nasties in the oil. ‘Its a mystery for now.

[dazmul1]

It’s more noticeable when cold but I can still hear it when it’s warm, definitely wasn’t there 2 weeks ago as that’s when my wife was last in the car, she got in yesterday and without me asking if she could hear it she said what’s that whistling noise?