I have a 1999 f250 sd 166000 mi & it has a code po266 cylinder#2 contribution / balance fault. !!!! does this code mean the injector needs to be replaced;; i had someone with a scaner check it & he said he has changed the valve cover gasket & that fixed the miss;can anyone help!!!!!!!!!!!!!! thank you for any help.does anyone know the mieage for the injectors for replaceing them!!!!!!!!