More injector issues

[lancinfish]

I was doing some truck maintenance since the computer has said I have a bad #8 injector. I changed the fuel filter, which was due. It had about 10,500 miles on it. When I was doing the fuel filter, I pulled the drain plug and was supprised to find that the plug had a gread deal of rust and other garbage on it. So I cleaned it up and it had eaten away at the metal of the drain plug. I am not sure what caused this, but it was nto that way when i changed the fuel filter the last time. If the garbage that had done this is making it by my fuel filters, no wonder I have a bad injector.




After changing the fuel filter, I no longer get a code that Cyl#8 is bad. it now says CYl#1 is bad. Do you have any opinions? Did I kill an injector by changing the fuel filter? do I have fuel pump issues? if so, how do I check the fuel pressure? There was a Shrader valve on my 7.3L adn I know ther is not one on this truck. Thanks