ever since I put my header on my civic I get a code 01, defective primary sensor, or primary sensor open. What is the problem? I bought a new bosch sensor since I couldnt get my factory one out of the stock manifold...My car seems to drive fine with the light on but it idles a little rough now.

have you made sure all the wiring is fine, maybe you scraped one of the wires on accident. If you replace the o2 Sensor with a new one, then it should be working just fine, also, when you installed the new bosch one, it most likely didn't have an oem hook up. so you had to splice the wires with the new o2 sensor right? I had to when I replaced mine with a bosch. I ended up having to switch the wires around and that took care of the problem. (this was on my old 97 EX)