For a 1989 420 SEL with 240,000 KM, my emission inspection shows :

At 40 KM/h (1384 rpm)
HC PPM 53
CO% .05
NO ppm 73
dilution 15.05

at curb idle (670 rpm)
HC ppm 43
CO% .00
dilution 12.00

I did have to fiddle with the mixture to get a pass. Do I need a new cat.? What would the readings be if I do need a new cat?

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1989 420 SEL