Man, I am so sorry...
I amswered that post at 3:30 after being aroused by a newborn crying!.. sorry..
the 420 is NOT the EGR.. it is "catalyst below efficiency"
Either way.. both codes point to a lean condition. still check for leaks around any vacuum tubes, gaskets (tb, EGR, IAC, UIM, LIM, etc) spray throttle body cleaner towards different areas of the car while it is running, and if it stumbles or stalls that is your culprit area! (the tb cleaner will make the car still when it gets sucked in to microscopic cracks.. avoid the air filter, obviously..)
Ray
