I took my Camaro to be smogged soon after I got it, and it failed horribly. I had the CAT and O2 censors replaced and it passed all parts except the last one, NO (PPM). The maximum allowable for NO is 484 @15mph and 711 @25mph, it measured 1065 @15mph and 1140 @25mph. Someone said it looks like it needs a new EGR valve, so I replaced that and took it again. On this last smog it passed the 25mph with a score of 703 but still failed for the 15mph with 791. With each repair it is scoring better and better. But we are out of ideas on what it now needs to pass. I don't have the money to take it to a shop.

Please offer your opinions on what it could be that is keeping this car from smogging.