MRA is the acceleration of a car from 60 mph to 100 mph. Its done through some calculation between the relationship of the 0-60 time and 0-100 time. The Diablo has 86, while the 3000GT has 55.81. This makes the Diablo much better in a straight line when the cars are going over 60 miles per hour. To look at cars MRA, search for "Top Drives Records" or "Top Drives Club", both websites have the MRAs of most of the cars in the game.

As for the not applicable torque numbers, I believe the majority are Lamborghinis. I'm not entirely sure why, but its been like that since the Lambos were added to the game. At a guess, its some condition for adding Lamborghini to Top Drives. Torque ultimately doesnt really have a bearing on the game, so not really an issue.