I just bought an 87 base model for a few hundred it runs but is running a little rough at lower rpms. I changed the oil in it, what should i do to smooth the motor out?

Seafoam?
Injector cleaner?

just for clarification, motor is a s4 6 port n/a

 

Check your throttle position sensor and make sure it is set correctly. After that set your timing. I'd also do a full tune up (filters, plugs, etc).

Seafoam works ok. You can also do the "water trick" or use carb cleaner and spray it into the throttle body while it's running. There's some vacuum lines you can undo and spray into the hole. You need a person to keep the revs up cause it will die.

 

If it's running rough, then do these first.
Plugs, plug wires, timing, TPS test/adjust and idle speed setting. Most simple rough running problems are solved by these. If its still running rough, then you probably need to give us some more information about the symptoms.