Gilly, thanks. Now you've said it, I'm pretty sure that's what it is. I hadn't thought of the heat shield, but the noise is exactly the same as a noise my dad's Audi made with a loose shield years ago. It's going in on Wednesday.

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JJ Rodger
2013 G350 Bluetec
1999 SL 500
1993 E300 diesel T
1990 190