In answer to your question, yes....all are normal. Get yourself some S.O.S. pads and scrub the carbon away.... That's what I do on my Solo Street Race Exhaust.
Solo Street Race exhaust
ASAP T2 stripes and badging
Windrestrictor V2 lighted in white
Windrestrictor lighted door sills lighted in white
DDM Works IC Piping
Undercar LEDs in white to match Windrestrictor
ZZPerformance dyno tuned - 286HP, 317ft/lbs of torque at 23psi of boost.