This car recently had a new catalytic converter installed. Also, its fuel/air mixture is not yet optimized but is in a "sane" range for the car (Mercedes specifies .5 to 1.5 as I recall).

At 15 miles per hour we have the following readings:

HC 153 ppm
CO 1.08%
CO2 13.9%
O2 0%
No(x) 1885 ppm

At 25 miles per hour we have

HC 150 ppm
CO 1.16%
CO2 13.7%
O2 0%
No(x) 2407 ppm

What stands-out to me are two things: (1) the NOX is out-of-the-park high. (2) the O2 is at 0%.

This car had previously run for about 400 miles with a very rich mixture and a CO reading of about 5%. The question is, do we have a bad catalytic converter or is the lousy fuel/air mixture causing all of this problem (e.g. do we need to lean it out more to get the catalytic converter to reduce the NoX). Or, do we have some other problem. This has historically been a nice clean running car. The fuel system has been overhauled. It has a very slight manifold leak but historically this did not cause a lean miss at CO levels under .6. One other variable is if the fuel system work, comprised of a new fuel distributor and new injectors, is suspect. The car runs beautifully-- smooth idle, beautiful acceleration, quite and smooth as silk.