My 91 240, 190k miles has same diagnostic codes as you since I bought the car. I changed the O2 sensor, plugs, wires, rotor, distributor, fuel press reg (FPR), cleaned throttle body (TB) and replaced TB gasket, cleaned/replaced flame trap and hoses, replaced air filter, removed/cleaned/inspected air intake box to ensure thermostatic valve worked properly (it did), reset Throttle Position Switch, throttle stop set screw, throttle linkage and kickdown cable. No change in code.

I sprayed carb cleaner and water at every conceiveable spot that could be the source of a vacuum leak, with no corresponding noticeable change in idle speed. I have temporarily given up on trying to find the source of the diagnostic code. One day when I get the energy I am going to install the new intake manifold gasket (a hunch) that I bought last month.

In the mean time, if I were you, I would remove the dashboard CE light bulb (if it makes you nervous). I AM NOT suggesting you attempt to deceive the inspection system, but I know that the bulb can be distracting and a safety hazard while driving at night.

good luck,