Help needed whining noise

Hi,

i have just brought a 2010 fiesta 1.6 diesel. I’ve noticed quite a loud whining noise when driving.

 It goes away when I engage the clutch but it’s there when either accelerating or even rolling (unless clutch is engaged). The sound is kind of like a dentist drill but not quite as severe.

i initially thought possibly a air leak from some pipe from the turbo or something but the fact it does it even without any throttle makes me think maybe not. Could it be that still or possibly a belt?

another issue which may or may not be related... when I take my foot off the accelerator it seems like the car still receives gas for between 0.5 and 1 second after.new to these cars and only just got it so not sure if it’s supposed to do that or if it is another fault but any help or recommendations would be appreciated.

i do have it booked in with my mechanic but he can’t look at it until next week so just after advise on likely causes from symptoms it’s showing and see if it’s something I could look at/repair before getting it to the garage.

appreciate the time!