renault espace - whinning at 20-30mpg

hi

i have a 1996 espace.

150k miles

went in for this service last week (150k miles)

car is now whinning in the 20-30 mpg range like a high pitch police siren noise of one note.. that varies its pitch dependant of revs.

seems to be rev depenendent as if you press clutch in & rev engine its still present.

however having said this car drives as you would expec.

any thoughts what this is, think it may be turnbo but strange it onply appeared after a service.

i would take it back to garage but they are not local so would to likely problem

many thanks