i bought a car with a 4-2-1 header and it dont have hole for the o2 sensor so would it be possible to drill the hole in any port for the o2 sensor or does it have to be at all 4.plz help

 

You definitely needs your 02 sensors. Just take the headers to an exhaust shop and have them weld on an 02 sensor. It is very cheap. If CEL remains, just buy an 02 simulator and splice it in.

 

thanks ice but could you give me some info as to what a o2 simulator is and does. ive heard about them but never been given a good explaination and how much do they cost?

 

what kind of car do you have. i know when i bought my megan racing 4-2-1 header, it had temporary bolts that you removed where the o2 senser goes. There should but a at the top of the header where its 1 pipe. and another where it meets the cat.

 

I'm not sure if these headers replace any cats on the car, but if they do, you will probably get a CEL. The o2 simulators basically just trick the car into the thinking that the cat is still there. These splice into the secondary o2 sensors, not the primaries. But, to answer your original question, the o2 bung will need to be welded where it can read the exhaust from all 4 pipes.