Failed Emission Test TX

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1989 190E 2.6L Gas/Auto Trans.

Failed Emission Test:

Low Speed Test Failures:

1)Hydrocarbons HC (ppm) 185 my car (162 limit)
2)Nox (ppm) 2139 my car (1227 limit)

High Speed Failures:

1)Nox (ppm) 1664 my car (1121 limit)

The vehicle has 195K on it, the engine was just dropped in from an 84K car, it has splendid compression at 180-190psi per cylinder.
I am almost sure that Nox failure is indicative of EGR problem. I dont know anything about Mercedes EGR system. What could cause HC to fail, only at low speed? The HC passed by 10 ppm on the high speed test.

Any ideas? I am selling this car and the interested buyer wont buy unless it passes. The emission tech said the idle was too high, about 1500 rpms. Is this adjustable? How?

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