Never threw a CEL since I got the car.
I take it to the dealership because although it's always been a loud engine, it sounds like a diesel lately.

They tell me there's nothing wrong with it and they hear nothing odd...

I got my car back after a week (Although I had a sweet loaner '07 A4 with 4k miles on it for the weekend).
It took them 3 days to tell me there was nothing wrong with it, and another 3 to put my engine cover back on.

I started the car up this morning (10 miles after I left the dealer) a CEL pops up!
WHAT THE SH*T?

I think they did something to my car. My 225 feels slower than before, but not limp slow.

What can I do / say?

 

damn take it back and tell them whats wrong. do you have any mods that they might blame it on or something like that?

 

The code would be helpful... that's exactly why I don't trust anyone to my car, sometimes not even myself