Audi A6 1998 model 2.4l v6
 

Can anybody tell me if this Audi has an idling air control valve and if so where is it located. I replaced engine in this car and everything was fine until the first day that I drove it. It started cutting out and now the idling is very poor. I checked every possible thing I could think of like timing, plugs, plug wires I even had a new throttelbody fitted. What else can cause this idling going up and down? I checked for vacuum leaks but found nothing aswell. Any help will be appreciated. Thanks Francois.