Originally posted by 90AccordEX4
If your NOx emissions are high then you are right it is probably the CAT. How bad is it? I just finally passed my SMOG test yesterday and was having the same problem. Try retarding the timing to 13-BTDC from the stock 15. That is how I passed. At 15-BTDC my NOx was 948ppm and at 13 it went down to 787. Max here in CA is 799 this time so I barely made it. So if you are within about 150ppm retarding the timing should do the trick. It lowers the peak cylinder temperature which reduces NOx emissions. Hope this helps...
I'll try retarding the timing as well. All three values that Ontario checks, the readings where 3+ times greater.
There is a fuel additive here call Gaurenteed2Pass. It contains menthol and helped my Camaro pass so I'm gonna try that too.