I had this issue come up with my Mobil-1 tune.
someone harped in on me saying, "lol why did you add ballast to this? It didn't need ballast in gt5!"
And im like, yeah, it also had like 200 less HP. RTFMM, lol!
Yeah, they turned a number of the lesser powered ones from GT5 into complete beasts. This makes them online creepers, as people with their nuclear Calsonic Impul's see a little old Mobil-1 come in and dont even think of you as a contender, and you find yourself head to head with them on the last lap and they say to themselves, "WTF?!?".
Needless to say, you show up in ANY GT500 in GT6 and you have the ability to control just as much as anyone else now. Evened up the playing field.