As of now, I have a 2005 Midnight Blue GTO, M6, with a Vararam OTRCAI and 245/45/R17 Nitto 555R on rear. Very soon, I am going to purchase a DiabloSport Predator tuner. Will this put me in high 12's? And what other mods should i do? (i want to avoid headers but it "is" doable.) Thanks.