1993 245 with 260k miles.

Here's what I know:
1. In Atlanta, emissions testing is not required for vehicles that are 25 years and older. My brick is 24 years old; this is the last year I have to get emissions testing.
2. 25/25 Test Results: NOx (ppm) was 1738; allowable limit is 878
3. 50/15 Test Results: NOx (ppm) was 1674; allowable limit is 970
4. Emission test was done after car was driven for 20 minutes during 40 mph neighborhood drive to run errands
5. Emission test facility recommendation sheet: "Possible causes of excessive NOx include faulty or clogged EGR valve, thermostat, old coolant, oxygen sensor, mass air flow sensor, incorrect ignition timing, incorrect fuel pressure, broken or leaky vacuum hose."
6. Car runs fine.
7. Never replaced catalytic converter
8. Recently had intermittent arc on coil wire at metal tubing on master cylinder.

Here's what I don't know: What I should fix to make this beast pass the test for the last time!

Thanks,
Cabbie