my problem first started a few weeks ago got a misfire code and a lean bank right side . changed the plugs. truck ran good for 1 day . code came back . changed the cops , all 8 . the truck runs good around town but when you get to 70 mph it starts to shake and sputter and the eng. light flashes . changed the fuel filter same thing.what else can it be?

 

Big problem area .
Did you change all boots on cops . Boots keep 30,000 volts from jumping to head . Swap injector on no 2 .
It is good form to clean out snout area of plug in cly to dissolve carbon that breaks plugs both on removal and installation .
What plugs are you using the newest is sp546 mc --sp515 were bad out of the box many times.
No 2 is passenger side 2nd in from radiator .
Oem cops are best they rarely fail just get corroded connections. Cheap cops were never good to me.
Plugs must be done correctly on this engine ,they are 5 inches down in there .
Use a very small amount of dielectric grease on ends of boots . Keep plugs and hands clean .If you use anti seize make sure it doesn't get near tip. Only good anti seize is nickel for its high heat resistance .It is a conductor don't get it on boots or porcelain .