Black stuff on my bumper around muffler?

I have a 1998 honda civic dx, we just rebuilt the motor, my car has lack of power which I considering it the distributor because as I'm picking up speed it cuts out power like it's not getting enough spark to about 3000rpms then picks up instantly. Do you have any suggestions? Am I wrong about the lack of power and it cutting out about I being my distributor? And what could cause the black stuff on my bumper around my exhaust

Black stuff must be the vtec

The engine is running much to rich, hence the carbon deposits on the bumper.