How many miles on the car? After installing the mileliminators, the PCM will not turn on the CELs for P0420 and P0430, those codes were caused by inefficient precats (there are instances when those codes could be caused by other issues). That will get you to a smog test. If it is the begininng of the precats going bad, it might pass the smog test. If it doesn't, then a new main cat ($520 plus labor) will help.
Read this.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=v6maint&Number=1196893&Forum=v6maint&Words=mileliminators&Match=Entire%20Phrase&Searchpage=0&Limit=25&Old=1year&Main=1196753&Search=true#Post1196893 
