Quote Originally Posted by nllnellie
i'm sure i can figure out what else is wrong. i'm only 600 away from passing now. and with the cat.... when i got a new one put on, it didn't help at all. it actually made my NOx worse by like 20 or something.
Did they replace it, or ADD one?

Your car should have a precat AND a cat, if it had the USDM D-series in it...If you only have ONE cat and no Precat then that may be why. That's why I suggested adding a second cat, though I meant it more as a joke than anything else.