The racing Modification is not readily available in GT3, unfortuneately. But that doesnt take away from the game one bit, IMO. This still THE best racing games out. Although... you can perform the stage 1,2, and 3 weight reductions, but no racing mods. Still the cars get suped to say... 1000 hp. whoo! hang on!
I usually keep my cars at lower hps tho, I think its unneccesary for any car to have anything over 600 hp. If you really know racing, you know its all in the tranny, to level out the horsepower to the likings of the car.
Anyway, this game is definately a MUST BUY.