I dunno what it is, but it'll do it when I have NOTHING on. It does shake more, when I'm on an incline, too.
I'm gonna try to get new spark wires, cause mines are the stock ones. I hope it helps.
I also tried resetting the comp., when I installed my intake kit, but that didn't help. At first, I thought it were my brakes, which could still be a possibility. I'll keep you guys upto date on what happens.
