[Beav]

I think the figures you show are a bit off, not many cars from '94 will blow a 68 HC. Our limits are easier here - 220 HC, 120 CO. Most decent running cars with some miles will aveage around 110-150 HC, exceptional cars will idle at 50-55 HC and around .2 CO, with a few even lower.

Anyway, HC is raw fuel (or oil, etc. in case you have a little oil burning going on) CO is poorly burnt fuel. NOx usually stem from high combustion temperatures. We don't normally deal with NOx or O2 here so I don't pay much attention to it. Usually it falls in line if the HC and CO are good and the EGR is working properly.

You failed to mention if these are idle figures or cruise figures, that will make a difference. If @ idle, look for a vacuum leak, it can cause a lean misfire which in turns raises the HC. It can also cause an elevated NOx reading. I found a leak at a very small check valve under the manifold, just behind the right side of the alternator. You might also try disconnecting or pinching off the PCV hose to see if the HC drops. You might also loosen the oil fill cap while it's running and see if there seems to be excessive case pressure.

You're not very far off from passing, it's probably something simple. I rarely see cats go bad and causing a fail problem - maybe one or two/year at the most. Most cat failures are meltdowns, not failure to 'light up'.