I happened to find that a connector near the engine on my A4 looks "unusual", I mean it's like eroded. (see the pic, marked by a red rectangle)

does anyone know what's that? Is it bad?

Thanks!
(you may see that from my question I really know nothing about the mechanics)

https://www.audiforums.com/forum/att...1&d=1226526716

 

Looks like a little oxidation of a plastic check valve. I wouldn't worry about it if the car is running fine. And even if it isn't I doubt that it would have anything to do with the outside of said component being weathered. It will never be that easy. Never.

 

It's a check valve and just because the outside looks a little messed up doesn't necessarily mean the function of the valve itself is bad. You can take it off and blow into it. Air should only come out one way. If not, it's bad and needs to be replaced.