I recently bought a set of headers from a guy on craigs list, everything was great, they were cheap. But they do not have a spot for an o2 sensor. Now before i do the task of pulling off a header, drilling a hole and welding a bolt to it, my question is, what will happen if i just go without an o2 sensor? When i swapped the motor i pulled out all the smog stuff anyways, so my check engine light is gonna stay on regardless. Is it a bad idea to run no o2 sensor? Thanks alot

 

The engine will run like crap and you will have terrible gas mileage. Go ahead and put the O2 sensor bung in there. Any good muffler shop can do that.

No, the SES light will not be on all the time because you removed the federally-required emissions devices. It only checks for the EGR valve and only while driving on the highway. But you'll have to watch out for the smog-police. And make sure you hang onto those devices. They'll be worth more than gold when the current government forces every state to do mandatory emissions testing like California does.