weird check engine light

Car is a 92 with the b18a block and using a ls head from 98, The factory ecu is chipped so in the car right now is a 94 or 95 ls ecu. Im currently getting a code 41 four long flashes then one short fast one im guessing code 41 change 02 sensor no reset ecu no change. Decided to try the factory ecu even though it chipped the code 41 goes away but now im left with a code 20 anyone have any ideas?

actually just checked they are both 37820-pr4-a11 ecus throwing different codes

Do you have a cat on your car?

Actually, we would need more info. What intake manifold, engine harness are you using? The 98 head is obd2, where the ECU would be obd1.