after doing some hard runs, I'll notice black residue accumulate around the rear of my car, all over the bumper, around my right rear tire area. I'm checking the tailpipe, no carbon build up. I'm thinking it might be my sucky ass tires. I don't see any smoke, I've had someone watch as I mash down. At WOT i'm running 11.9 -11.6, thats not rich..