Q: Truck has occasional putter but not a misfire when giving it gas at an idle. 3 years without driving. Bad fuel mix or spark plugs?

Depending on storage conditions, ethanol content, and so forth, fuel will expire in 2 to 6 months. If fuel has sat in a tank for 6 months, and the car has not been used during that period, there is no question that the fuel tank should be drained, the in-line filter replaced and possibly other fuel system service will be needed. In your circumstance, which involves a 3 year period of non-use, the fuel injectors should be removed from the fuel rail and sent out for professional cleaning. Mr. Injector, located in Idaho, is one source of this service. Each fuel injector on your car has a tiny internal filter basket and these are removed and replaced during such service. Once the fuel system has been restored, including cleaning of the injectors, the engine condition would be re-evaluated and any other deficiencies addressed. To obtain fuel system service, including injector removal, cleaning, and re-installation, just refer to YourMechanic’s fuel injector service request page. The mechanic will come to your location, evaluate what you have and let you know what the optimal strategy will be but in your case, to reduce diagnostic headaches going forward, and ensure the best possible operation of the engine, you need to service those injectors because they are likely partially blocked with the oxidation by products of gasoline that has sat in them for 3 years.