As far as headers go, they have to be stamped with a CARB# for Cali. It's kinda funny too, those #'s must be expensive cause it sure jacks the price of things up.
Same goes for intakes...must have CARB#.
Then you have to smog it to what ever the the motor, in this case, would have had to pass for it's year. (91) Cat, charcoal canister, EGR, etc.