Well; I’ll answer my own post on the oft chance that some other poor SOB with the same problem will stumble across this in the achieves.

Error/Fault code 16 (16 blinks of the LED) is for a faulty EGR Valve. I applied vacuum to the EGR valve with the car running and found that it would not hold vacuume or make the engine run rough, an indication of a faulty EGR valve. I replaced it with a known used god one that I had in my parts hoard, cleared the code, and all is good. This information applies to my 1990 300SEL

Many thanks to an old friend that unexpectedly came through with this information.