i have a 90 gs with a b16a2 engine. having codes thrown, just gonna buy some new o2 sensors. my question is, do i need the sensors that would go with the 99-00 si civic? or the 90 gs... i'd assume the si, but im not sure... im still learning shit. Denso starters, alternators, iridium plugs, fuel pumps and glow plugs or this Denso starters, alternators, iridium plugs, fuel pumps and glow plugs also, should both be in the header? or can i place them b4 and after the cat. im not familiar with this shit. let me know. any advice is appreciated.