I've got a 2000 VW beetle, 2.0 L. The Check engine light is on. Also, the temp line remains on for a long time and comes on off and on. The car idles rough sometimes. Sometimes I push on the gas and the car doesn't go. Sometimes it runs perfectly. After I warm it up for a long time, it runs better. I took it to Autozone and they hooked up the OBD and said that I was misfiring on all cylinders and there was also a code for a fuel(?) problem. They couldn't tell me exactly what is the problem. I disconnected my mass air flow sensor and the car idled better, but still ran bad. I cleaned it with CRC electrical parts cleaner and it still runs bad. I've got new plugs. I had the problem before I changed the plugs. I don't see any errant sparks from the plug wires. Any suggestions? Thanks.

I have excessive nox emmissions which caused a failure on the state safety sticker test. What could be the problem, Cat. converter or Oxygen sensor.