Renault Laguna 1.9Dci 02, horn like noise + sluggish?

Hi,
Yesterday as i was driving i began to hear a horn like noise (almost like a vuvuzuela) when my revs get around the 2000rpm mark. The car stutters a little at times and when i get up through the gears there is some black smoke comes from the exhaust.
Was hoping to get rid of the car in a month but want to sort this on the cheap!