I had my car washed yesterday and when I got home I found a curved black plastic trim piece appox 2 inch X 14 inch shoved under the front edge of the drivers seat. The P/N is 996.521.317.00
The car is an 04 C4S. Can anyone tell me where this part goes?

 

Not sure of the part #, but it sounds like the plastic trim that fits over the seat slider rails, under your seat. It snaps over the metal rails to give a more seamless look

 

Sounds about right, as the car wash person had adjusted the seat. Thanks.

 

Thanks for the suggestion, but that is not the part. Here is a pic of the orphaned porschepart

 

LOL, I had the same part fall off mine. I never could figure out what it was for.

 

Go to the dealer.

 

You can call dealer to have them look up by part number. They'll tell you what it is for or at least where it goes. This may save you a trip to dealer.

 

The part in question is called the 'seat module hider'