Thats it alright. I think my car launches harder with 2 people in the back then what it does with just myself. The extra weight most deffinetly helps. I've got 2mth old Koni Shocks and 4mth old Pineapples, my last bet is new Dunlop FM901's to replace the Falken ZE502's. If they dont fix the problem (or dramatically improve it) im not sure what else can be tried. I just wish somebody could give a reason as to why it happens (too hard, too soft, wrong setup, etc).