I failed a smog test in CA (1992 Corvette) and the results came back that the EGR valve is not holding pressure. It failed on nitric oxide emissions measured at 989 ppm at 15 mph and 1329 ppm at 25 mph.
The repair for that is cheap, but the mechanic is also saying my cats are bad, which are mondo expensive as you well know. But what I'm wondering is if the cats could perform adequately if the EGR valve was working correctly. The mechanic didn't mention anything about back pressure, but the temperatures measured in the two cats are: #1 520*F in front, 217*F in rear, and #2 532*F in front and 202*F in rear. I understand that these temps are not good, but is it possible they would come down if the EGR was doing its job?
I've had never-ending problems with this car and I'm just trying to get it up to code so I can sell it and be done with it, so I'm not concerned with the long term health of the vehicle. I'll be sure to let the next buyer know about the cats though. I'm not a crook, I'm just trying to cut my losses down to a minimum.