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I did go out and buy a bottle of Techron though to help clean the engine a little
Then you've already done a more than sufficient "fuel injector service".
This is just something the dealer is trying to sell you to make a few $$, unless there is reason to suspect clogged injectors there is no reason to pay them to do this, especially not as a routine service every 15K.
The fuel you are using already contains detergent additives to keep the fuel system clean, it's present in all grades but usually there is more in premium. An additional shot of Techron once in a while will supplement what's already in the fuel but that's all you need.
The only other things you should do to protect the fuel system and injectors are-
1. Change the fuel filter at 30K as per the service schedule.
2. Don't routinely run the tank down below 1/4. Doing so may shorten the life of the pump and also may allow any dirt at the bottom of the tank to be sucked up into the system.