My car had one right under the headers and another one after the flex pipe. There ar definitely two. HondaEater

 

I think Hyundai started making all their cars with Cilfornia emission for ease of assembly, just a thought. rolleyes.gif

I extended sensor #1 and made the extension for #2, I just need to have a muffler shop weld in a bung for #2 in the pipe after the cat.

I drove the car to yesterday after the extension and of course the CEL is still on but I'm stii only running one O2 sensor.

 

Both O2 sensors are back in action. I'll reset ECU (disconnect battery) tonight.

Maximus, what did you end up doing about your header?

 

Surprise< I drove it about 10 miles & CEL is gone

 

The CEL for that should be "self fixing". As soon as both 02 sensors stared working...it should shut itself off.

 

ok i know this might sound stupid, (im sick and sleep deprived), if you get a full exhaust done,... the 2nd cat and flex will need to be removed and replace by another cat with bigger tubing right???

 

Yes, once you get headers, as much of the stock exhaust as possilble should be replaced with larger diameter tubing. 2.25 will preserve your low end at the expense of some top end. 2.5" tubing will give you more top end at the expense of low end torque.

 

dam i was going to go all out and go for a 3 incher,... im guessing i sacrifice even more low end for more gain at the top end?
oh well
thats 2 months from now
lol

 

anything over 2.5" is way overkill for an NA motor, unless you are reving to over 10,000 RPM and moving some serious volumes of air. Hell most turbo's only have 2.75 to 3.5" exhausts...

 

For a n/a cars with four cylinders you don't want to go anythng larger than 2.5. If you have turbo bigger is better most likly 3 inch. 2kwagon whick exhaust header did you use?