California Emissions Test fail

My '92 Stealth failed CA emissions. The test is run on a small dyno at both 15 and 25mph. My car failed the 15mph test badly - it did better on the 25mph test. Hydrocarbon and NOx levels were way high. CO was OK.

I took it to the dealer, who wanted to replace the intake manifold. I told him NO, because I didn't think that would have a large effect on the emissions. I plan on checking the EGR valve, replacing the plugs (65K miles on them) and checking out the catalytic converter. Does anyone else have any ideas of what could be wrong or other items I should check?

Nope, sounds like you have it covered. I'd get new plugs, check the EGR and cat. Also, check at your local auto parts store. There is a bottle of stuff that actually guarentees you will pass IF you are still stock. The bottle/can actually has a red 3000gt on it, ironically enough.