Okay, we've been over this a bazillion times: the TUNED CARS from GT5P were NOT Racing Mods. They were Heavily tuned versions of the stock cars with the Aero Parts seen in the GT Auto videos.
The Racing Modifications are taking the car and making it into a race car. As seen in the TV Spot, you can see that one of the Corvette C6 cars becomes the GT2 Corvette C6-R. That is not the same thing as the the tuned car from GT5P.
I would also assume that the Racing Mods can be tuned a little more than the stock versions. We'll have to have someone do the experiments to confirm this, but I can promise you guys, racing and tuned are not the same thing.