Ok, found another prob with my mustang, to start it is bone stock nothing removed (that I know of) it starts and runs fine but smokes just a bit when I rev it up good, when it is parked I can start it and let it idle and look on the ground where m exhaust turns down at and the ground is clean, but if I rev it up and go look at the groung the ground is a little wet and a has a black color to it, what could this be???