I have a 92' corolla DX, and recently failed TX state emissions inspection. We have some Nox test, in which I failed with a difference of 4500 points (standard is about 1200; I got 5675).

I haven't done any repairs yet, but does anyone have any suggestions? Is there any hope for that big of a difference? The repairman said new catalytic converter is the best bet, but doesn't know for sure if it'll cover 4500 points difference.