Looking over my 2007 wrx this weekend I noticed the stock downpipe is missing a bolt that goes to the tranny. I was inspecting because if I drive at lower speeds within an area that echos the sounds of the car I hear this rattle - between speeds of 15mph to 45mph. Would this missing bolt contribute to this noise? Guessing the tranny vibrates a bit and perhaps hitting that flange with the missing bolt on the downpipe? I notice this noise only when the windows are down and the car shifts great. Thanks in advance.