[Tyson Schmidt]

Nhromyak is right. Lower octane fuel is easier to ignite. That's why high compression engines can knock with low octane fuel. The low octane fuel ignites from compression. Diesel effect. High octane fuel is less volatile, resisting compression-ignition. This is why lower octane fuel will give you lower emissions. Less unburned fuel out the tailpipe.

CIS can easily be adjusted lean enough to pass the sniffer, even without smog equipment installed. Provided, of course, that all is well with engine and state of tune.