Got up under the car to tighten the exaust bolts down and noticed i forgot to connect a hose, but where does it go?

 

That is for the split air pipe. It connects to yoru exhaust, that is assuming you have a S4 na there.

 

no he has a s5 91

 

Ahhh then unfortunately I am at a loss, id run out to my S5....but its abotu 10 miles away so I cant check visually, sorry man.

 

its the air pipe for the exhaust but is unneeded since the air pipe does not control the 5/6 port opening on the s5. You can put a hose on it and block it off with a screw or you can attach it to the exhaust manifold.

 

Well actually if he is still running emissions, the split air pipe is used to help heat up the catalytic converter to help emissions. So it is needed, unless he is running no cat.