1994 Ford Probe excessive nox

1994 Ford Probe 4 cyl Front Wheel Drive 213000 miles

failed emmissions twice for excess nox and elevated hc, replaced plugs, flushed with injector cleaner in tank and in intake and added guaranteed to passin tank any suggestions, runs resl good no miss idles low once in a while but never dies. No codes on or check engine lite so egr system should be ok cleaned pcv