Yes, I did search, but didn't find any answers. I bought an O2 sensor awhile back as routine maintainace, but couldn't get my old one out so put it off. I did the mpfi swap and I didn't have it running right for a little while, so there was more motovation to change it. Although still couldn't get the old one off. It threw code 1 once or twice, but went away. I decided to buy a header since I was guns have to take the manifold off. Got everything swapped out, and it started throwing a code when it got warmed up, now it always does it when it warms up. I changed the O2 sensor again, but still does it. It drives fine untill just before it gets all the way warmed up. Any suggestions?

 

Your timing is off and the sensor is detecting it in the exhaust. Check your cam timing first, then set your ignition timing.

Don't forget to reset your ECU to clear the code.