After my 2002 E430 4MATIC is warm, when I stop at the stoplight I hear occasional 'popping' noise that sounds as if it is coming from the rear exhaust area.

Any ideas what this might be? The car has 46k miles on it.

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE