My 85 240 passed emission test two years ago (that is only 18000 miles ago). The readings were HC= .24 gram/mile (limit was 0.8), NOx=1.0 grams/mile, CO=2.2 grams/mile (limit is 15). To pass, I installed a new Catalytic Converter, replaced the ICU, O2 sensor, plug wires, dist cap, Air Mass Meter.

But now, the readings are HC: 1.8 gram/mile, NOx: 2.3 gram/mile, CO=7.2 grams/mile.

Can the catalytic converter be bad so quickly? I am looking for the parts or adjustments which will make the most impact on the test. I know that , just the night before the test, I cleaned up the flame trap, throtle. I regapped/ cleaned the spark plugs (not replaced). I have set the timing to 12 BTDC was 10 before). I adjusted the CO content using the AMM screw and recheck idle. I have not replaced any ignition components such as wires, distributor cap , rotor).

Please let me know what you would do in this case.

Thanks