i have noticed here and there on this forum that some of the folks running the brembo gran turismo big brake kits are possibly running your rotors in the wrong direction. i spent numerous years building brake upgrades for tilton engineering with AP & BREMBO. the theory behind either drilled holes or slots is that they meet the pad at the outer/top edge first. so if your brembo hole curve backward and hit the pad bottom first. they are backwards. take a look at your brembo install book and verify. if your rotors scoop the air and pull it in towards the center and not pull from the center and pump it out, they need to be reversed. generally solid drilled is the exception because they are not vented. holes and grooves channel dust and gase's, nothing to do with cooling