That is not a good idea don't move your o2 sensors and anyways if you do get a code that is what these are for http://roadracemotorsports.com/store...products_id=36
And if you're still scared of not passing emissions: KEEP THE CAR STOCK
But I have not gotten any codes since the header was installed (well only misfiring codes, but that is another story), and I still have the stock cat back, I can't give you any performance gains estimations because my car has been misfiring, but what I can say is that don't go for the cheapest header, look In the 100+ dollar range or just buy a used rrm/ obx/ kamikazee header.

 

I was thinking of getting a header and downpipe for sound and to spare my cats anymore wear and tear, so I can swap them back on to smog the car.

I thought the o2 sensor is used in conjunction with the MAF to tell the car how lean or rich the car is running, so eliminating the sensor or modifying the input from the sensor sounds iffy. Am I way off here? Wouldn't performance suffer because of that?

I am also concerned about excess backpressure from a full exhaust system.

 

the oem lancer header has the precat built into the header.... with a aftermarket header the precat gets eliminated but the ss header has the o2 bung on the header to put the sensor back in. now about the code, rrm has the cel eliminator you instal on the main cat witch shd eliminate the cel. i know magnaflow has hf cats that are federal legal 49 state (cali-legal 50 state if u reside in california) that will pass emission testing ...

i dont think you will have a problem passing as long as you have the main cat installed.

 

allright thanks guys!

 

hey jujkiller, do you think you could post up a pic of the underside of your car? I purchased the exact same headers, and plan to keep the cat back that is currently on the car. I just want to see how you fit it in there.

Thanks!
-Steve

 

@mq1991


Not the best fit but It works, It sits a little lower than stock.

 

Thanks for the pictures! That confirmed what I was thinking to be the problem with my car..

It seems that the 2004 lancers are welded to the main cat, where the 2003 and back are a bolt on. which makes it harder to get it connected.

Ah well, do you think a muffler shop could cut off the flange and weld it to the cat? They shouldnt charge too much for that... i hope... lol

thanks again for the pics!