1996 Toyota Corolla HC remains high even after tune up

1st smog test failed: HC was high (few points higher than max at 15mph)

2nd smog test passed: HC was still high (few points lower than max at 15mph)

Did a tune up to replace spark plugs, wires, cap, rotor, etc just to make sure will pass smog test.

3rd smog test failed! HC was high (few points higher than max at BOTH 15mph and 25mph)

Replaced O2 Sensor

4th smog test failed! HC was way high (MAX:64 MEAS: 100 at 15mph)

Replaced CATCON

5th smog test passed. HC was still high (MAX: 64 MEAS: 49 at 15mph) CO and NO were much lower than before

6th smog test at Test Only station. HC failed at first trial at 15mph and passed on 2nd trail with above average number (MAX:64 AVG:7 MEAS:24 at 15mph)

It's a relief that my car is finally passed this round. It's the first time I've problem in passing smog check. It seems like HC is still a problem. The technician told me that he "ran" the car well for 2nd trial.

Any clue? Just want to prepare myself before next smog check.

Thanks.