Living in California, I know a couple things about smog issues and stolen catalytic converters.
The computer in your truck is assuming there is a problem and is throwing a code, hence the CEL. When a CEL is on, your computer goes into a default mode. You are definately not getting everything out of your truck that Toyota programmed in.
The tweekers are stealing catalytic converters on Toyota trucks out here at a frantic pace. Because the trucks sit higher, they don't even need to jack up the car to get it out. Numerous solutions have been tried here to stop the thefts, most of them unsucessful for the most part. There is a guy here that manufactures a bolt-on plate to prevent the tweekers from being able to reach the cat.
Anybody that doesn't know what soap tastes like, has never washed a dog.