Ive noticed when my car is ticking over, the exhaust note instead of being constant oooooooooooooooooooooooo its more like oooooooooooooooooooo ooooooooooooooooooooo lol if you no what i meen. its like its not idling properly but its not getting any higher in sound. I looked at the rev counter and the needle does move but only very slightly.