Code is for emissions and it's not the gas cap "already changed" distributor changed 3 times also changed plugs, wires ,cap and rotor,and also fuel filter.Motor turns over and used to start after a while of turning over.It also was missing when on the highway before it stopped starting.We very rarely drive this truck.It sits under the carport most of the time.We have only put maybe 25000 miles on it in the past 4 years.Mechanics have told me to change the things that have been changed.Also shops have changed part after part and it has only gotten worse.Was also told it might be a vapor leak in the fuel system.Any ideas would be GREATLY APPRECIATED.