what could cause my injectors to go bad???

[stevecast]

i have been trying to trouble shoot my 99 ranger 3.0l. i have found 2 bad injectors #3 & 6. i replaced them and started the truck it ran good for a couple seconds and started missing again. if i unplug the injector the idle does not change making me think it went bad again. is this possible? any help would be greatly appreciated...

 

[fivespeed3.0]

Sounds like it might be the electrical connection to the injectors

 

[--weezl--]

or possibly lack of a fuel filter and terrible gas

 

[stevecast]

after a ton of internet research. I think I may have screwed up.. i have had the ranger for about 6 years and hell if i knew it was flex fuel? 8th letter in vin was a
V. so i am now hoping that i have not screwed up the ecm or anything else. so from what i have read it has happened to others where 2 injectors have gone bad. also being that i was not the person driving the ranger, one injector could have went out first...

also i have changed the following .. fuel filter plugs(motorcraft) wires air filter pcv .

thanks for the response guys

one more thing what on the engine or any other sign other than the V in the vin would show it is flex fuel.
thanks