Over the last week I've noticed that when i come to a stop the idle is dropping as low as 400rpm and sometimes stalling. When I first start the car from cold it idles at 2000rpm initially and settles to 1000-1100rpm. It only starts to idle at 400 after I've driven her for about ten minutes, but if I turn it off and start again the idle returns to normal so I'm assuming its not due to the engine being hot. Also noticed tonight that when idling low, if I rev the car the lights brighten. Not too sure if its always done this, but i only noticed tonight. Any ideas?