I have 1990 Honda accord ex, it failed the inspection. The inspector told the car is running
rich and showed the blinking light which produced code 43. I then replaced O2 sensor,
fuel pressure regulator, fuel filter. Spark plugs, distributor and rotter. Also cleaned EGR shift valve. None of it produced the any result. I don't no where to look. I really need help.
Also, Got my exhaust leak fixed.

I checked the fuel Injectors connectors and its resistance which was 2.5 Ohms and all is fine. Also I did sound check by removing the connectors one at a time and all sounded the same when engine is running.

Symptoms of my car now stands at low idling (500 to 600 ) when parked or N.
Automatic Shifting the gear at 3000 to 3500 RPM. CEL comes when gas peddle
is hold at 3000 RPM. I have cleared the code many times and still coming with
code 43. My Honda has 220K miles.

 

Code 43 is kind of generic.
Would you happen to have the emissions test results? Or is it just a pass/fail test?

Check the wiring for the O2 sensor, on the EX models it is attached to that little pipe under the car, if the harness is damaged/grounding out it may cause a code fault. Look for chaffed wires/damaged insulation.
If EGR was at fault you would have a lean misfire condition which would increase all of the emissions outputs. NOC CO HCs. Check at the top of the page in the Accord FAQ on how to clean out all the ports. The EGR valve usually does not foul itself, but the feeds to the runners do.

 

common issue resulting in code 43 is an exhaust leak causing the oxygen sensor to fuel dump

you can seafoam the motor to see if there is an exhaust leak while looking for white smoke billowing out of the exhaust anywhere from the exhaust manifold to the oxygen sensor