Chuck Gould wrote:

:else as valid. It is interesting to note that at the state level a
:laboaratory in California that is certified to conduct testing for
:California Air Resource Board compliance purposes measured some
:differences in combustion with vs. without a device installed. (And
:yes, the lab could have made an error).

CARB compliance means that it doesn't increase emissions, not that it
improves them. That's the only thing you can conclude from the study.
There's not enough data to draw a stronger conclusion. You don't know
what the normal variance in exhaust emissions for that engine is.
That can be surprisingly large, particularly since they're not
controling for engine operating temperature.