i have a 2003 lancer es. would hollowing out (taking out honey comb) my catalytic converter cause my check engine light to go on because of the oxygen sensor??? and if the check engine light does come on will it actually decrease the performance instead of enhancing it, or will it just show the error and not decrease it? also what are the tricks to getting off the nuts that hold the cat to the pipe, ive sprayed wd-40 on it, used an air wrench, and used a socket wrench with a pipe on the end of it for more leverage and its still tight as hell and refusing to budge ?

 

That is basically the same as a test pipe. the O2 sensor reads off of the oxygen content emitted from the engine. Since the filter is removed from the cat conv. (honeycomb), the o2 sensor will think there is something wrong with the engine and will throw a code when in actuality the filter was removed.

 

drill out a spark plug non-fouler and screw it into one that is intact... put the O2 sensor into this contraption and then put it back in the piping. this is for the 2nd O2 sensor btw.

if you can get the car up on a lift or if you can get down in a pit you will have a fighting chance with the bolts and the O2 sensor--otherwise you might as well give up right now before you round all the bolts off.

personally, i'd leave it alone. if you want to get rid of a cat get a new header without a cat. this way you will still pass emissions and you will still be removing a cat. the header was way easier than even just attempting to remove my 2nd O2 sensor when it was on the car and i couldn't get all the way under it.