Well, all of our cars run rich, and that is GM's solution to keep the engine safe. Thats what we have to deal with until you do a custom tune on the car. You are gonna get smoke from the large injectors. Driving a little faster will help clear out the fuel system by allowing everything to work at full tilt, but it will not solve the black spots on the back.
We need more boost!
K&N CAI, GMPP exhaust w/XTC 3" d-pipe,
Ported stock exhaust manifold, B&M Shifter
Stage 2 w/2.8, DC Sport sturt brace,
Torque brace, CAB's, poly Trans mounts,
225/40/18 BFG KDW2 tires
GM drilled rotors w/Hawk Pads