I have a 2000 zx2 s/r and when its at idle my rpms drop well under 1000 and then returns but after driving when I come to a stop it does it again(5spd manual) and at times it has even cut-off I have been back and fourth to the dealership they have replaced spark plugs, wires, and Iac which . But still same result, they didn't find anything in the computers memory that states somethings not working properly but somthing is wrong it also happens while I am in a sharp turn and when I have both headlights and fog lights on while I am braking for a hard stop. the rpms get really low and the car almost cuts off and most of the time it goes back to 1000 rpms other times it cuts off any suggestions??