thanks for the suggestions Jeff.
I took the car for inspection on sunday. I figured best to just see how its doing and attack the problem from there.
It passed. but HC and NO at 15 mph still at borderline and NO at 25mph doubled from last time.
I learned that Santa Clara Valley(and LA basin and San Diego) are the county that requires enhanced smog check. and some county like Lake County doesn’t even do bi-annual smog check. Like you said the car must follow the type of test it registered at.
Yes e36 has cyclone separator too. it seems that also maintenance item on 100k+ miles car.