You say the injectors "look horrible". If your talking about the black carbon on them, that's normal. You can't tell anything just by pulling an injector an looking at it. It's not a spark plug.
Since you have them out, why not just send them off and get them rebuilt. NO, before you ask, you cannot do that yourself. Might as well pull the pump and have it rebuilt too. Pull the head and rebuild it. Maybe do a compression check, before you pull the head. The motor may just be worn out. Would probably be easier to do a compression check through the GP holes with the injectors in. Did you ever try giving it a snort of either just to see if it would start? You didn't answer the question as to whether anyone has had the pump out of the box or not? Maybe someone had it out and didn't put all the shims back in. Or coated it with silicone like I see all the time.
