Hey Just curious but does anyone know the difference between an f22a4 and an f22a6?Is it all in the head(valves,cam etc.)or is it something in the bottom end that gives it the ten hp difference?The reason I ask is I am going to have my a4 head off for a valve job and stuff(valve seals leak)soon but I will scrap it for an a6 head if I can bolt on the ten extra while I have it apart anyway.Any help would be great.