I need some help with my NOx emissions... I have tried most of the steps in the other threads but I cannot seem to lower the NOx emissions

When I took the test, here are the numbers
HC 27@15mph (max 110) 29@ 25mph (max 85)
CO 0.00@ 15mph (max 0.71) 0.04@ 25mph (max 0.59)
NO 789@ 15 mph (max 772) 703@ 25mph (max 711)

As you can see... I am just barely failing. I have tried to remedy the problem but to no avail. I have tried changing the O2 sensor and the EGR valve but that dropped the NOx by like 2-3 pts. I had my CAT changed the last time I had trouble smogging it, and it looks to be working properly (I could be wrong). I do not have a timing light so I cant check the timing to see if that might be the problem. When I hooked up my vacuum gauge to the EGR system, it reads 0 but when i put my finger on the vacuum line, i feel a slight vacuum at idle. Not sure what else to do... so I ask for your help. Thanks

 

welcome to the best Third Gen Camaro/Firebird site on the net.

all your readings look really good, but you may be just a little on the lean side, or your cat is working really good.

odds are you EGR system is working, otherwise NOx would normally be a lot higher.
a decarb probably wouldn't hurt if you haven't done it.
i think you may be able to get NOx down enough with timing.
where are you at? i ask because in some states like California you can't mess with timing much, Cali only allows + or - 2 degrees from factory specs. if you can pull 2 degrees of timing that may well be enough.
what fuel did you have in it when you tested? going up a grade may also help out on NOx.
if can do both, pull some timing & go up on fuel grade im pretty sure you'll pass.

 

Thank you for having me. I have a VIN E camaro btw since I didnt mention that before so I have a 305 TBI engine. I will definitely look into the timing. The cat is 2 years old... it did wonders for my last smog check (believe me... that was hellish). I also need a little insight on decarbing, i have actually never done that. Yes i do live in Cali... so I have to keep the timing +/- 2 degrees so that i can get it into inspection. Since the gas spike, I have only put regular 87 in it, but I will splurge a little bit to get it to pass. Thanks for your help