How to increse the air fuel mixture ratio.

I have a 92 buick century and I dont' know where the screw is to increase the air fuel ratio, and i forgot do i screw it in or out to increase it.

Ok I found out its in the computer, the adjustment so I guess its going to eb expensive.

Yeah, the air/fuel mix is in the ecm, you could possibly chip it if your looking for more fuel, depending on the motor, there is one for the 3.3 and the 3.1