Black stains on White bumpers

I know how it sounds but humor me. I have an LT1 based car that is supercharged. It is tuned under full boost to be at 11.5 afr or so. I have a white car and I have seen in my upper rpm ranges under full throttle I get a fair amount of black smoke from the exhaust which is staining the back bumper. The car is not burning or useing oil and the black seems to be carbon or soot. I wanted to pull some fuel from the tune but am not sure which table to pull from. Maf or WOT vs RPM. If it is the Maf tables, which table?

Its the % change to AFR at WOT table, like this but this of a 12.9 AFR, assuming the VE tables are correct. You're using a wide band right?
http://www.monodax.com/forums/attachments/tunercat-jet-obdii-hardware-software/708d1196217709-simple-pe-table-lean-out-clipboard.jpg
I ended up painting my white bumper like the CETA TA, no pics but looks nice.