Sucking noise when i press accelerator pedal?

I have a ford focus 2006 when i tap the accelerator or press it quick i get a sucking noise from the engine bay, this seems to go hand in hand with the car running lumpy and not smooth when i de-accelerate it tends not to run on it jerks, and also when i slowly go around things like roundabouts it tends to jerk, any ideas ive replaced the breather pipe from the throttle control to the sump, but not sure where all vaccum pipes are etc etc got haynes doesnt help.