I have a 1989 Pontiac Firebird 2.8L V6. The check engine light came on and the code was 45. It makes sense because you can smell that it is running rich. I changed the air filter, and the housing looked figuratively like a rat's nest. I know there are many different reasons why it is throwing the code, but where is a good spot to start trying to fix it? How should I go about diagnosing the problem?

 

These are from the 89 Camaro FSM but I don't think there would be a difference.