No, surprisingly, there was very little carbon at all. I was expecting thick deposits, but I only saw a light coating. I gently brushed and scraped it off and vacuumed it out.

Took the truck for a nice run on the highway and up a mountain road, and, at least so far, those dreaded codes have not returned.

Also noticed something that I'd never really paid attention to before. Under normal driving conditions, the temperature gauge barely rises. I'd say that unless towing, it's usually at about the 1/4 mark or less. Today, on the highway before the mountain road, it easily climbed to halfway. Of course, on the way home it behaved the same as always.

Is it related? I doubt it but it was something I noticed that was different. Also, the truck seemed to run a bit smoother than it used to.