Emissions Gurus please read and reply!

[Andrew]

Brothers,

I need help. My 87 190e 2.3-16v (replaced motor with a Euro spec) has now failed emission testing twice...the first time I expected it.

The catalytic converter was clogged up, so I kinda helped it "breathe" a little better and knew the car would fail...I wanted to see how badly, though.
Here are the numbers for the first test: (just the high speed)

----------------Standard-------Current Reading
HC(ppm)---------173--------------------415
CO(%)-----------.98--------------------0.20
Nox(ppm)--------1323-------------------382

As you can see, only the HC reading was through the roof.

Now, here are the numers AFTER I replaced the cat:

-----------------Standard--------Current Reading
HC(ppm)---------173--------------------43
CO(%)-----------.98--------------------0.00
Nox(ppm)--------1323------------------1974

Someone please tell me how in the heck the Nox shot up like that!

Could a new catalytic converter cause this emissions nightmare?

Note:Over the past few days, my car will, without warning, shut off. All I have to do is restart it, though...could this have something to do with it?

Gurus, please help!

Thanks,
Andrew