I am going to rip the beast out soon.

I have an 88 SE (S4). I am currently fabricating a new pipe to connect my header to my catback. No more cats or gutted shells to create turbulance.

I pulled the hard pipe that runs along the exhaust and connected to the old main cat. When I pulled it free, I noticed a very thin rubber hose also connected to it.

Where does this hose go and what does it do?

Mind you, my car is 8' up in the air on the hoist, so I can't look under the hood right now to trace it myself.

Everything I have read in old threads says I can remove the air pump without any problems as long as I have a dual belt pulley. But, I haven't found anyone comment on that little hose.

 

the little hose connects the 2 pipes toghter, it comes with most aftermarket cats

 

those opperates the 6-port actuators. You'll need to either weld a bung into your new exaust or operate the ports electronicly.

 

I will look into the electronic method, but I will prolly just weld it back into the new system.

So much for getting rid of the air pump right now

 

you can still get ride of the air pump, it doesn't do anything for the aux ports on s4's just for emmisions. the bung you would weld in the exhaust would be basicly a leak leading to the aux ports tom provided the needed pressure to open them. if your exhuast doesn't have enough backpressure they won't open and you'll need to do the electronic activation which is what i did and recomend