First, here are the test results and limits.

Hydrocarbons 79.1 ppm /189.0 ppm PASS
Carbon Momoxide .44%/1.21% PASS
Nitrous Oxides 1468.9 ppm / 1374 ppm FAIL

1985 244 DL B230f

I read through the archives and it appears that any of the following could cause this problem:
1) Excess oxygen entering the cat - exhaust leak ahead of the cat
2) Bad Catalytic Converter
3) O2 sensor maybe, but not as likely as above. I checked it recently using a multimeter with the method described in the FAQ's and it was fine.

The exhaust isn't new by any means, but I don't think there are any leaks ahead of the cat.

The cat was replaced about 2.5 years ago with a cheapie from autozone. I suspect this is the problem.

In addition, I beleive there is a vacuum leak somewhere. However, not a large leak because I have checked vacuum at idle with a gauge and it is in the acceptable range but idle is somewhat rough.

Simply looking for a little advice, but right now leaning towards dropping 125+ bucks on a new cat.
Thanks in advance.