Check for vacuum leaks on the hoses, and PCV valve, and you'll most likely fix your problem...

What kind of mileage is on the thing?

 

If it is until it is warmed up, it sounds as though this may be an EGR problem... Cheap and easy thing to check first after inspecting all of the vacuum lines. All you'll need is a new gasket, some sensor safe carbon cleaner, and possibly an old toothbrush.