I don't think anyone here "knows" how to do it. I've heard of it being a server glitch, but I've seen it alot. I doubt if someone does know they will not tell
Just a note, KOF straight up sucks at CoD4. I had him on my list a while ago (1 month) and always played with and against him. 95% of the time, I was on top. He did rank up the majority of his time, which is why he is ranked so high.