I received this from a Vibrant rep:
"In response, this is a commonly asked question and is misunderstood by many. Our exhaust systems are constructed from T304 stainless steel which is one of the highest grades of stainless you can find. Be that as it may, everyday exposure to the elements over time can cause T304 stainless steel to develop iron particles on the pipe that rust; which shouldnt be mistaken as penetrating rust. With T304, the surface oxidation / iron particles that you see will not penetrate the pipe whereas pipe that is NOT stainless steel will be subjected to actual penetrating rust after exposure to the elements."
Mine was rubbing on the bumper lip as well. Piled up some foam pads on the edge of the heat shield above the muffler. The pads press down lightly on top of the muffler. Used Kartboy hangers up front for clearance over the cross member and stock hangers on the muffler which create more space from the bumper.
Not to be all negative about it...
Very noticeable power increase over stock.
Sounds good with silencer in (otherwise too loud for me).
Looks nice with perfect angle and protrusion of muffler tip.