1989 S-10 Running Rich (Code 45)

I have a 1989 Chevy S-10 4 cylinder 2.5 throttle body fuel injected engine. I recently got a code 45, that states my engine is running rich according to the oxygen sensor voltage. I have replaced the injector with an OEM injector. The truck runs better, but I am still getting the code. What else can I check?

most thing s that would cause a rich mix will show up as a hard code. things like a bad map ,temp sensors, O2 sensor. but a mechanical leak like a stuck fuel press.reg or leaking gasket in the TB. or [Ive seen this on a couple gm TBI 's]a cracked TB houseing under the press reg resi won,t show up on a scan.and drive u to drink. Check fuel press if you can first to see where you are .and the look for fuel leaks into air stream.it sometimes makes a slurpping sound inside the air horn if its severe enuogh.stethescope or 5/8 heater hose can help you hear better.Bear Paws!!!