Just wondered if anyone else has notices a noise from their exhaust when you switch the engine off, each night when I drive home from work the cars cold and been sitting usually about 9 hours parked up with the engine off, I drive about 10 miles through stop start rush hour motorway and city traffic to get home, when I park up switch engine off and walk to my front door I can hear a metallic "tink, tink, tink" noise which I'm guessing is coming from the exhaust? Just wondering what the hell is making that noise, why its making that noise and if its normal/supposed to do that?