I'm pleased this has generated some healthy discussion. Chris Martens has raised an interesting point regarding a possible change to later ignition modules having fewer programs. My testing seems to indicate that for my both my 1990 M102 and M103 EZL-KAT AUS versions, there are only a limited number of R16 values that give a valid result, and open circuit R16 is not one of them.

Duke2.6,
My results showed that the shorted R16 condition (like the open R16 condition) resulted in the most retarded ignition. I must repeat that the greatest effect of R16 is at higher engine speeds and minimum vacuum (high load or WOT).

jasondew,
I would interpret your air/fuel ratio result of a more complete burn as possibly being due to more advanced timing allowing longer time for combustion prior to the exhaust valves opening. Others might have greater expertise in the combustion process.

Obviously experimenting with R16 is inexpensive and worthwhile. If my original post inspires those who have tried the modification to, at the very least, check their car with a timing light, then I am happy to have posted this thread. Thanks for reading and contributing.

Greg

__________________
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.