Commenter Alcohol explains the Check Engine Light

the CEL is often triggered by the trim being out of boundaries rather than actual lean condition.

With all vehicles however- the concern is not likely to be in closed loop operation- the concern likely would be in open loop such as WOT that you might go too lean unless the ECU has a learn ability for open loop. Larger injectors are often used in performance applications to insure full power and stoichiometric conditions at WOT.

Interesting. You know Al, I used to be an actual, honest to god automotive engineer, and I don't know this stuff. How do you know all this?

The Scangauge will tell you if you are in open or closed loop, in addition to trim and O2 sensor data.

I have to think that the way that I drive, I am very seldom in open loop.