Starting in the 1069 model year or a yar or so later, it was popular . . . as an emissions decreaser orientation . . . to delay any sort of spark advance related to the normal vac advance until after the car reached about 25mph or so, or was in high gear (for manual transmission vehicles). In other words, a "spark retard device".
There are two things. 1) it was a part of the factory emissions control device package and should not be "tampered with" according to federal emissions law from back then.
2) As the car can now be titled as an "Antique" in most states, no emissions checks of any kind.
Was it effective to reduce NOx emissions? Apparently it was when new, but probably something only related to "the numbers"
In reducing emissions, the HC and CO are easy, just make the engine more efficient. Which also can increase the "heat of compression", which increases NOx emissions. To decrease NOx, decrease the "heat of compression", so "retard the spark advance" is the easiest way to do that (with an existing engine). Hence, selected spark retard of the NOx speed sensor.
Your call as to if it can be deleted as the car is older and not in CA any more. At this stage of the game, I rather doubt somebody would even look for each iten of any car's emission system for emissions compliance. Things like the snorkel "hot air" air cleaner and ducting to the exh manifold heat stove are much more apparent.
Just some thoughts,
CBODY67
