On most of the foreign cars with aftermarket exhaust there is always a black residue on the rear bumper. I never had this issue with my american muscle cars. Is this a foreign car issue. Will this be an issue with the Z. Would love the imput.
the black stuff is carbon buildup and is normal (happens to every exhaust including stock). it shouldn't be excessive and if you keep up with normal car cleaning you wont notice it. On my old car i never got anything on the bumper but occasionally the tips needed some cleaning.
i always thought that carbon on the bumper was attributed with an engine thats burning oil. I had an old civic back in the day that would get carbon on the bumper. It would go through a litre of oil every 2000k
Really given'er you get more carbon on the back than just cruising.
ninja edit: Though that car had a magnaflow catback 4-1 race header and was decatted so maybe the decat could have some impact as well? Maybe a bad cat/poorly performing cat on a car could give the same effect.