Hello. I'm a little disturbed but not really suprised that my first car, an 87 245, has failed its emmisions test today. Can somebody help me with the results. I'll explain the symptoms.

The results:
the CO passed
the HC(hydrocarbons) failed by a few points
the NOx failed miserably.. more than twice the legal limit.

I am suspecting the coolant thermostat of being bad. here's why. My car never fully warms up. It is getting cold now in NE USA, but even after a significant warm up or a drive, the temp gauge in my dash only reads at about 20%.

other than that, could it be the torn pre-heat hose?(i didn't think that would effect emmisions if the car was warmed up)
I just did a pretty comprehensive tune-up after i bought it.

Thanks for any help. I could use some advice into what i should replace before i get a retest or cause any damage to the cat or engine by a lean mixture.