D.E.Q. Tests Passed, and HOW!

[STORMINORMAN]

Boy, it really has been a long time since I've posted to this Board!

Just ran the '91 420SEL (@145Kmiles) through the Oregon Department of Environmental Quality's latest battery of emission tests: time to renew the registration. What really surprized me were the results!

TEST a). HC ppm Max 220 b). CO(%) Max 1.00 c).CO+CO2 (%) Min 6.0

RESULT

@idle 0 0.00 15.2
659 rpm

@load
2,500 rpm 3 0.02 15.4

This totally blew me away, as it is often necessary to run older cars through three or four times (usually after multiple repair$) in order to get a pass. I do use premium gas exclusively.

The plugs are recently replaced non-platinum Bosch, the oil & filter was changed last week, the coolant has been changed to G-05, the air filter has about 5k on it... Other than this normal maintenance, the car is running on the plug wires, distributor cap and rotor from the previous owner's last dealership major service of 3/99, almost exactly 50K miles ago!

Is this typical of W126 cars? Should I leave "well enough alone" at the 150K point or go with a new distributor cap, rotor and plug wires?

Cheers!

p.s. I don't seem to be able to get the results to properly allign with the test parameters, for some reason: the readings at idle were 0 for HC, 0.00 for CO% and 15.2 for the CO+CO2%. At load (2,500rpm) they were 3 for HC, 0.02 for CO% and 15.4 for CO+CO2%