codes p0401 and p0420 what else can i change to make this work on 1997 Saturn SW2

what are the codes i have change these parts already still getting this codes

by in Victorville, CA on December 19, 2011
3 answers
ANSWER by on December 19, 2011
Most likely those parts shuld not to be replaced at first place as i said below.
ANSWER by on December 19, 2011
YOUR EGR SYSTEM HAS SERVERAL PARTS TO IT, WHAT PARTS HAVE YOU ALREADY CHANGED.ALSO YOUR PO420 CODE PERTAINS TO CATT EFF. BELOW THRESHOLD WHAT HAVE YOU CHANGED THERE
ANSWER by on December 19, 2011
401 is an egr code that may be a clogged passage rather than a bad egr valve. stop throwing parts at it and have it cheked correctly. 420 is a bad cat. it must be replaced. Roy