Help with noise/lag on monte carlo

Hi please can someone help, im getting what sounds to be like a vibrating noise when you first rev it at low end revs (especially when cold) it sounds like an old diesel car and its a 14 plate. I was thinking maybe the turbo or injectors. There is no funny coloured smoke but there is a bit lack of power on lower end sometimes to the extent of needing to change down a gear like the car cant pull as well at low revs.