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IM THINKIN BOUT GETTING THOSE KAMIKAZE HEADERS FOR MY 03 CIVIC SI HB FROM PTUNING. HEADERS ARE JUST A BOLT ON REPLACEMENT RIGHT? WILL I HAVE TO MESS WITH THE O2 SENSORS? DO I NEED A DOWNPIPE, WHATS THAT FOR? PLEASE HELP A CIVIC BRO OUT, IM TRYIN TO LEARN ABOUT THIS STUFF BY DOING IT MYSELF. PROLLY NOT THE BEST IDEA BUT ILL LEARN. THANKS

 
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yo.. lay off the caps dude.. most people dont wanna read something thats all in caps..

anyways, it should be a direct bolt on..

 
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i dont know about the si, but on an ex, you don't have to mess with the o2 sensors; a straight install. On the EX, the downpipe goes from the end of the headers to the catalytic converter, which is actually welded onto the downpipe. Then the exhaust. On the LX and other models, though, the catalytic converter is part of the header. In that case, in replacing the header you take out the cat, thus making the car smog illegal and you have to get an o2 simulator. I'm not 100% sure about everything I've said, so someone correct me if I'm wrong. I don't know anything about the si though. And yeah, you need to find your CAPS key.

 
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hmmm...i'm not sure about the SI, but my bro told me that on his rsx, the header would replace everything, meaning no o2 sensor....i'm not sure if this is really the case though.