a lazy O2 sensor may also contribute to high NOx. The EGR is on the drivers side of the intake (has a black round plastic cover over it). With the engine idling, place your finger underneath the valve, against the diaphram and lift the diaphram. At idle, the engine should stumble or die. This tells you the passages are clear. If you have a scan tool, you can watch the EGR duty cycle and the percentages should increase during light to medium acceleration. This tells you the computer is sending a signal to the EGR solenoid. If you disconnect the vacuum hose to the EGR valve and connect it to a vacuum guage and drive it and you should see vacuum on the guage at light to medium throttle. Next, with the help of a friend, start engine place foot on brake and select drive. Then you again rest your finger under the diaphram and lightly throttle up. The diaphram should move up as you throttle up and down as you release the throttle. If all thes these test pass, next look at the O2 sensor and then the cat.
