2001 transit whining/droning noise

[1985goldie]

I have just bought a 2001 t280 swb transit and at speed it seems to make a loud droning/whining noise? i dont know a thing about them and was wondering if it could be serious. it doesnt do it unless im at at least 60mph. also the van only does 80mph tops and sounds like its gunna blow, how do i know if the turbo is working (i cant seem to hear any turbo whistling) and whereabouts is the turbo situated on these models? Thankyou.