I am going to buy a 2006 tC from a friend but he has a header in it. the check engine light is lit. he says when u take off the header, the check engine light goes off. is that true? he told me he could take it off to show so me. i'll do that too just to make sure but its just that it take a while to do it and i work alot.
Thanks alot guys

 

search from now on please.

your OEM header is where your catalytic converter is. now before your catalytic convertor, you have an o2 sensor, and then after the catalytic convertor, you have a secondary o2 sensor that detects if the catalytic convertor is doing its job.

since he header you would want to put on will not have a catalytic convertor in it, it will think that your catalytic convertor is not working and will cause a CEL light. it isn't a big deal until you have to show up for emissions inspection.

to prevent this, you need to run some sort of anti-fouler on the secondary o2 sensor to trick it into thinking the catalytic convertor is still there and functioning.