Just replaced the small smog filter - I'm not sure its neccessary on my 89 S4. There is a round hole at the front of the receptacle that houses the filter and a round hole at the bottom. That's it, no tubes or pipes connected. Should there be? Car runs great, should something be attached and where would it be attached. Thanks for any info.

 

It should have a short downward pointing intake pipe and a central pipe leading to the air pump. If you have a functional air pump, you probably don't want to suck debris into it and the filter should prevent this. If your air pump is absent or de-functionalized then the filter doesn't matter.

 

Thanks Dave - is the air pump neccessary for proper operation or just needed for Calif. cars?

 

It's complicated. The catalytic converter is designed for air pump input. It may not last as long without the air pump. Theoretically all the smog stuff is required for resale and for federal epa compliance. Your car will run fine, probably better, with no air pump and no catalytic converter. It's your choice.