I've been having a problem that started out as a rough running engine (like it was missing) when it was cold and got better as the engine warmed. Lately it has gotten worse and runs rough even when warm (but not as bad as when cold). I get no engine diagnostic codes when this happens. I am replacing plugs and injectors tomorrow but after reading some other posts think this might be a fuel pump issue. Any other ideas of what it might be or things to check (I have limited diagnostic capability)?