I noticed my car was running terrible and I heard this very loud sucking noise under my hood and found this!



It's connected to two vaccuum hoses and was sucking air for all it's worth...Idle was a lot better when I just plugged it off with my fingers.

should I just block it off or was it connected to something important?

 

What did that piece look like before?! Hmm.. Do you see any hoses hanging around? I'll look at mine when I get home...If there are no responses I will give you a shout!!!

 

I looked for hoses everywhere and couldn't find anything and I don't remember what it looked like before...does someone with an s4 N/A have any good pics of their enging bay around there...it's right behind the TB

 

That's the thermovalve. Its job is to apply vacuum to the dashpot that controls the #2 secondary plates, which closes them so you can't romp on the engine when it's cold. Coolant passes through the thermovalve and when it heat up the vacuum is cut and the throttles spring open.

The pictures too blurry to see what's actually wrong with it, but I presume it's broken and is causing a vac leak. Assuming you're smart enough to treat you car nicely when it's cold, removing it and plugging any holes should fix the problem.