[josefresco]

It seems there's more to it than just badly tuned - it seems how to drive also effected the results:

"The most surprising thing we found was how broad the range of emissions was," says Evans. "As we looked at the exhaust coming out of individual vehicles, we saw so many variations. How you drive, hard acceleration, age of the vehicle, how the car is maintained – these are things we can influence that can all have an effect on pollution."

Not sure how they can tell "how a car is maintained" or "how you drive" from spot checking 100K with a roadside probe... anyone have thoughts?

[sukilot]

They are speculating , but saying it isn't just the car's "genetics" (make model and production year)