After I got the car back, post retest failure, the NOx went up from first test. 4.4 to 5.3. Shop said I need to replace the EGR valve and the Intake manifold...$1600 plus to 2 hours of shop time to diagnose. No one has suggested the O2 sensor. I was told the possible leak in the A pipe wouldn't be the probable cause for failure.
At no time since I have owned the car (4 years) has the engine light come on...but after I got it back today the engine light came on before I made it home. Is this a case of something put back together incorrectly or connecting the computer for diagnosis reset something???
The car is still running great, but hesitate to take it on a "beater run" with the engine light on. Will keep posting updates