Not only that... A-Spec was a very rough approximation of what finally became "Performance Points". A-Spec was horribly unbalanced, and sometimes gave you 200 point races that were ridiculously easy and some 100-150 point races that were ludicrously hard.
Performance Points are more refined in that they take into account more factors than A-Spec and give a more balanced field. Yes, there are some cars that come off better under Performance Points, but it's not to them having a ridiculous power or weight advantage (you can trim PPs to get almost any car to the same power/weight/grip ratio), it's just that it's easier to make them handle and accelerate better with the limited control you have over transmission, suspension and tires in GT5P.