My son in law purchased a 1987 v6 with a miss in the engine. we have changed the plugs, wires, fuel filter under the car and it still has a miss. Put a reader on it and it gives the following codes.
23 intake air temp sensor out of range/low
32 egr circuit fault
34 map sensor signal out of range/low
44 oxygen sensor lean exhaust

got any ideas where to start ?

Disconnect the battery for 10 minutes and see if the codes come back after a drive.

cleared the codes, and fixed the vacuum lines, and now have a code 44. will anything other than a bad sensor cause this?

replaced the o2 sensor and still get a code 44. any ideas?

Code 44 means the sensor value was out of range which "might" be indicating lean exhaust. O2 sensor is possible but now that you have the O2 sensor ruled out and can look at other things that might cause lean exhaust OR the circuit thinking it is.

1) Recheck for vac leaks

2) Check for exhaust leaks before the sensor

3) Check for broken wire or dirty/damaged connector to O2 sensor. You might also disconnect the wire and measure that there is at least 0.35V between the connector and chassis ground - if not there may be a break in the wire or the ECM connector end is bad.

4) Fuel lines leaking, bad fuel pressure regulator, or clogged fuel filter (but that was replaced). Someone else will have to chime in about whether bad fuel pump itself will partially give out here.

Anyone know if a clogged injector will cause only code 44?

Seeing that the code is a lean exhaust, I would start looking for a exhaust leak. Check at the cross over pipe. Listen for a slight tick, run your hands around the pipes, when engine is cold. You may feel air blowing past your hand.