I would agree that RT doesn't have an effect. Tire slip might have a effect to a certain extent. I know that I have left the light and after reaching about the 40ft mark the tires lost grip and went up in smoke. I had to let off till they caught again and then back in the game. The ET was around 15.7 but the miles MPH ended up at 103. I normally only make around 99MPH with a decent run. It really depends on how much time you spend in the best power range for your car. If you spend more time under or over you're bound to lose ground. Like I said it really depends alot on how good of a driver you are if you're going to base anything on timeslips from the track.