1989 Chevy Camaro Oxygen sensor lean code 44

First I'll need to know if your engine is Fuel injected or carbureted.

When you have a lean condition, either your 02 sensor is bad, or one/more cylinders isn't getting enough fuel.

If it's injected, then one/more of your injectors could be sticking/clogged. You fuel pump/pressure regulator could be failing.

If it's carbureted, then a 100 different things could be wrong inside of your carb. Also, the fuel pump could be failing.

The first thing to check would be your fuel pressure. (The procedure and specs would depend on what kind of fuel system you have)

If fuel pressure checks out, then you'd have to check for correct operation of the carb/injectors.

Finally, check your 02 sensor for correct operation.