You guys all overlook the most important factor. The fact that Jermey *loves* the Veyron makes it the fastest car on the track
Technical wise, Veyron should be slightly faster than the Zonda F anyway. It's AWD and has much better acceleration and braking so the Stig should be able to brake later and accel out of corner earliers.
As for weight of petrol, don't worry, half of the tank will be gone by the time the Stig finishes the first lap