I think some of you guys are overestimating what this thing can do.
It's just a metal airfoil that goes in the intake after the air filter. It's supposed to swirl the air, but it has no mechanical movement. It can't force any more air into the intake. As a result, it can't cause any harm to O2 sensors, sparkplugs, or anything else, but I personally don't see how it could do any good either. The reason the K&N filters work is it increases airflow over a paper element by reducing restriction. The Tornado Air is something you put in the intake, so in effect, it even acts as a restriction.
It takes a supercharger, turbocharger, or nitrous oxide to increase the amount of oxygen that gets into the combustion chamber.