I failed emmisions again on my 2003 Pontiac Grand Prix in Wisconsin. Still EGR flow

[catergirl]

insufficient detected.? The first time I failed it was the EGR. Then I had it replaced and the tubes cleaned and stuff total cost with part $135.00. How could it fail that again? My service engine light went on as well. Emmissions said it would fail if the engine light was on. Now this auto mechanic was not on their list of mechanics but he has serviced my husbands truck as well as my car before. I don't have much time before I have to go again which would be failure 3 if i don't pass. Yes my mechanic said he would look at it again but I was just wondering if anyone had any ideas why this would keep occurring cuz you guys out there always helped me before with great results !!!! Thanks