:yeahthat:I think you just need to clay-bar the surface, and seal it with some good wax. It's usually just some contaminant, brake dust, rail dust, small corrosive particles that are the result of vehicle and road wear.
Mine was the same but it was rail dust. Just get a good quality clay and free up a good amount of time because its stubborn. Before you clay it, give it a good hand wash, then run your hand accross the surface and again after you clay it. If done right, its like night and day. You can feel all the dirt and contaminents in your paint before you clay it and after, its like a baby's bottom :thumbsup: