I am having problems passing the emissions test over here.. My results are consistent even after changin the PCV valve, plugs and O2 sensors. Gas mileage is great, no engine codes (it is even above rated MPG for the car) and everything seems fine so I don't suspect the EGR system.

I suspect it is the catalytic convertors and other people think so too.

My readings are:

Limit Reading
HC ppm 68 154 FAIL
CO% 0.38 0.37 PASS
NO ppm 501 1092 FAIL

Does anyone also think it is the cats? If so, are the precats important in these cars? I know in some cars they play a miniscule role. Can I get away with just changing the main cat? Also are the cats just bolted in or are the welded as well?