Any idea what causes this?

Does it die or want to die when you mash the gas to the floor from idle and stopped, or mash it to the floor from 50 MPH cruise conditions, uphill or on level ground, etc.? Is this when the car is fully warmed up? Deos it actually die, or does it recover and smooth out? It is important to identifty the conditions under which this happens and exactly what happens; it can mean different things are wrong.