Chevrolet Repair: Engine running lean, throttle position sensor, vacuum lines

Question
I have a 1991 S-10 with a 2.5 liter engine.It is running lean,the check engine light code tells me that too.I tried injector cleaner and a new throttle position sensor but neither one helped.I have checked the vacuum lines and replaced a couple of questionable ones.I plugged off the line to the EGR valve and it made a big difference.
While checking the wiring connections I noticed that the ECM is a factory reconditioned one.
Any suggestions on what else to try? Any help would be appreciated,Thanks,Rod

Answer
Hi Rod, Two things that come to mind. The 02 sensor, it could be sending a bad reading to the ecm. Try disconnecting it to see if it runs better, if so replace it. The fuel injector, I have only seen a couple do this but they can make it run lean by not spraying enough fuel. You can only replace this part,cleaning doesn't work.

Hope this helps

Have a Nice Day    Mark