Originally Posted by 5soko
What your hearing is the exhaust flap closing and opening. Your sounds to be a little extra loose.
What you can do to cure this problem is the 'golf tee mod'.. This will disable the valve from opening and closing. I have disabled my valve since i bought my car, i pinched the black wire that goes to the actuator on top of the exhaust tip that was in the video, and zip tied it. This stops air going to the actuator, hence stopping the closing/opening action.
Or tell the dealer that your valve for the exhaust is bad and see if they will warranty it, problem not.
My car sounds exactly like this at startup and that's what I always assumed it was, too.
I have thought about having it looked at at one of my maintenance services but I have a modified exhaust so I figured they would just blame it on that
It sounds like a chain rattling.