Roy,
I honestly haven't noticed that much of a difference. I always found that the track preparation was much more of a factor in how I ran than the tire temperature. I have noticed that a burn out does not help at all, and that dropping the tire pressure also does not help. I used to spend so much time doing burnouts, or adjusting the pressure to try to get the most grip, and all my best runs were without a burnout and at about 30psi air pressure.