There is an adjustment screw for idle air mixture  and a screw for idle
speed.
Check out www.clarks-garage.com for details.

Try FQS position #4
http://frwilk.com/944dme/fqswitch.htm

This will retard the ignition advance a few degrees and you should pass
easily. In the past month, I have advised two others with higher NOx
numbers than you and they both passed.

Typically, high NoX levels are caued by higher than normal combustion
chamber temperatures.  High combustion temperatures are usually the result
of a lean burn.  A lean burn can be caused by a malfunction with, or a
mis-adjustment of the engine management system, low fuel pressure, or an
intake/vacuum leak.

High NOx problem solved!
My thanks to all those who offered advice.

As suggested by PowerP...@frwilk.com, I adjusted the FQS to position 4
(see http://frwilk.com/944dme/fqswitch.htm for details of switch
positions). I could not find the Bosch FQS tool so I made a tool from a
golf tee using a file and sandpaper. Worked.

My car is a late 1985 944 with 247,288 miles on the odometer. The
results of the failed smog test and the later passed test are indicated
below.

The test results of the failed test were as follows:

             at 15 mph        at 25 mph
             (1818 rpm)       (2021 rpm)

%CO2         14.7                 14.8
%O2           0.2                  0.1

HC (ppm)
Max.         135                  110
Ave.          41                   29
Meas.        130                   85

CO (%)
Max.        0.83                  0.44
Ave.        0.13                  0.11
Meas.       0.63                  0.34

NO (ppm)
Max.        1136                  966
Ave.         399                  332
Meas.       1135                 1030 (FAIL)

where Max. = maximum allowable
Ave. = average emisssons for passing vehicles
Meas. = amount measured by test station

The results of the test 1/13/06 (with FQS switch set to 4):

               at 15 mph       at 25 mph
               (1739 rpm)      (2031 rpm)

%CO2             14.5             14.6
%O2               0.5              0.2

HC (ppm)
Max.              135              110
Ave.               41               29
Meas.             116              109

CO (%)
Max.            0.83               0.63
Ave.            0.13               0.11
Meas.           0.39               0.33

NO (ppm)
Max.            1136               966
Ave.             399               332
Meas.            832               828 (PASS)