I would be surprised if it were the piston pin.

I have never heard of someone being able to diagnosing this by early when it is an early failure.

I would suggest you take it to another shop that knows your engine and is familiar with its sounds.

How many miles on the engine?

Where do you live?

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)