check engine light on;codePO138 set on 2001 Chevrolet Monte Carlo

replaced:O2 sensors,spark plugs,wires,intake manifold gasket and head gasket inless than a month;code returns & light comes back on. what now?

Asked by for the 2001 Chevrolet Monte Carlo
i hope this was not for that code. a lot of replacing.
138 indicates rich condition. could be a fuel pressure regulator, mass air flow or coolant sensor.
i think you may need a second opinion from a shop to track it down and help you.