hi dave, try looking for any splits in the pipes comeing from the airflow meter, normaly on your left when opening the bonnet, as they perish over time,split,then suck in air causing the car to run like a dog. mind you im no mechanic but this happened to one of my cars in the past. i taped it up tryed it and it ran fine so i then replaced the pipe. hope this helps you mate.
jason h
March 2008