Emissions failed

Ok. I just bought a 1984 chevrolet corvette. The cat converter had been replaced and the guy I bought it from hadnt had it in his name more than a year so naturally I assumed (I know, I know) that he got it smogged to transfer it into his name. Not an uneducated guess entirely. I mean he did have to smog it to transfer it but assumeing it was done legitimately was based on the new parts. The fact that he speaks very broken english didnt help the process, but here I am. Going back to him as California law dictates would be more hassle than it would be worth I'm afraid due to the language barrier. Well now for my question.

I guess I should just post the results from the emissions test that I had done some two days ago and see what you might be able to deduct from them:

15 MPH results:
CO2% 7.70
O2% 9.69
HC(PPM) MAX. 128
MEASURED 105 PASS
CO (%) MAX 0.80
MEASURED 0.83 FAIL
NO(PPM) MAX 1106
MEASURED 70 PASS

25 MPH results:
CO2(%) 8.15
O2 (%) 9.11
HC(PPM) MAX 103
MEASURED 76 PASS
CO (%) MAX 0.60
MEASURED 0.76 FAIL
NO(PPM) MAX 936
MEASURED 79 PASS

Over all it failed as you can see. What would cause the CO levels to be high? Barely I might add. Also what would cause the NO levels to be so low? Well under the limit. Should that be a concern? I just need to know what component would cause these levels to be off. Is it possible that what ever is causeing the CO level to be high could also be causeing the NO level to be low?

Thanks
Allen Pinney