So ive got a 99 si with a 98 LS engine in it, currently its got one O2 sensor down at the cat and an OBD2 to OBD1 conversion harness to the ECU. Obviously this can't pass smog, so I want to get it legit if its possible/reasonable.

From what I understand I need another O2 sensor on the top piece of the header (I need to replace the header anyway so its not a big loss), an OBD2 LS ECU and possibly a knock sensor, or did 98 have a knock sensor?

thx in advance