My youngest had a composite score of 148 on the WISC at age 7 but, like your ds, really does not appear PG/HG. In her case, we have a couple of thoughts that may also apply to your ds:
1) An IQ score is a picture of a given day and, while further testing does warrant the belief that dd has a HG+ side, I'm not sure that she is PG. Scores can, and do, go up and down over time. A child who tests PG at one point may always be gifted, but he also may have been tested at a point in time when he was at his highest and may not be "as" gifted as that one set of scores appears.
2) My dd has inattentive type ADD. I wouldn't rule out 2e as others have mentioned. Honestly, knowing that 2e is in play doesn't change the kid. She's still erratic, not particularly interested in learning, and performs below her ability. I have managed to push both her and her school to do more and she's performing well above grade level in some areas where she probably would not have had they just ignored the HG part of her as they seemed inclined to do, but will she ever perform like a driven HG/PG kid? Probably not unless something major changes.
FWIW, both my dh and dd11 have ADD (inattentive) and both of them don't enjoy reading the way dd13 and I do. They get distracted mentally while reading, read very slowly in relation to their fabulous vocabularies and comprehension, and just don't get drawn in the way they do when watching a movie, for instance.
