what does the small pipe from the cat due on an S5 motor? i know it controls the aux ports on an s4. would it be ok to remove it and not lose power?

 

that is how the air pump gets the air into the cat

 

It supplys air from the airpump to the catalytic converter and it has nothing to do at all with the operation of the auxillary ports on a series four car.

The catalytic converter needs that pipe. If you leave it off or disconnected it'll ruin the catalytic converter over time. They cost a lot plus a ruined catalytic converter will clogg up and reduce hp.