At 20K miles the car is broken in. Did you remember to turn off traction control? What are you using to measure your 0-60 time, maybe its only good for comparison purposes between runs on the same device (you can't compare a gtech run an a magazine run).
If its not the traction control and you are bogging on the launch its probably driver error.
If its not the traction control and you are bogging on the launch its probably driver error.