i was reading through the tech articles on 5.0 mustangs and super fords online and they had a couple of cylinder head installation articles. in one of them they put a set of edelbrock alum heads on a mostly stock 5.0 and they only gained about 19 rwhp. in another one they put afr 165's and i think an intake or a cam i cant remember and they only gained like 40 something hp. is something wrong with that or is that just how it is?