The intention of my reply was not to instill buyer's remorse in any way.
But I personally don't see a need for extended warranties and I have chose not to purchase them.
I honestly think you are in a good position with the choice you have made.
You seem to have bought a sound truck and at this point you should be enjoying your purchase, without reservation.
Since you now own the extended warranty, if it were me, I would plan on using it whenever the opportunity presents itself.
Having any repair that is covered performed at a dealer will almost assure that you will be able to recoup some of the cost of that warranty, due to their often higher repair costs.
However, if someone is willing and able to perform their own repairs on lessor items, they soon realize that the cost of those repairs is a lot of times close to, or even less, than the $100 deductible and it is not worth the time and aggravation of having the dealer do the work.
I'm talking about smaller things like water pumps, alternators and things like that.
But, in your case, I would be prepared to see what a repair like that would cost me if I did it myself or let them do it.
Extended warranties are designed to drive more repair business into a dealer's service department than toward a DIY'er or small shop, since covered repairs most often are not covered in those cases.
I do not use dealer service departments since I have a very good local shop that does any repair that is too involved for me to do.
At the very least, if I had bought the truck you did, the first thing I would do is purchase one of those plug in devices that turn off the AFM system.
I would do this right away.
With the plug in device, you are not having any physical work done to the engine that may void your extended warranty in any way.
The plug in device will simply turn of the AFM system while it is plugged into the ODB diagnostic port in your truck.
You allow the AFM system to function normally whenever you remove the device, like when you take your truck in for service at the dealer.
There is no trace of what you have been doing, as far as the dealer is concerned and the damage the AFM system could have been doing all along is minimized.
Secondly, make sure you have your oil changed regularly, maybe even more often that the truck's built in oil monitor suggests.
On average, my truck likes to have me change the oil every 7500 miles or so.
I would make sure I was changing the oil at least every 5000 miles, or even less if you so desire.
The trucks that are running the AFM system seem to report their engines tend to use more oil between oil changes.
Make sure you are keeping an eye on the oil level on a regular basis and you add oil as needed to keep it full.
One of the symptoms of an engine that is beginning to show signs of problems related to the AFM system seems to be engine misfires caused by oil deposits forming on the spark plugs in the engine cylinders that get turned off when the engine goes into 4 cylinder mode.
Keep an eye out for any check engine lights that may indicate that such a problem is occurring.
Really, other than that, keep up with your normal maintenance and drive your new truck and enjoy it.
You have made a good purchase, no regrets.