The reason to have the OEM LSD in the MR2 is for accelerating through turns, not drag racing.
It helps with oversteer, by planting the rear end when you apply throttle coming out of a turn. The LSD will get the power to the wheel that needs it depending on which way you are loading the car.
Most LSD are not going to make a big improvement in the MR2 for drag racing. Why not? .... because the OEM set up already puts power to both wheels. It is quite possible to leave "dual burn out" marks with the MR2s open diff.
With proper driving, I have seen MR2s hit 1.7s in the 60' with and without LSD.
Now if you get the more solid type of LSD (forget the name for it), you will neet a slight benefit for launching, but it will be at the expense of handling power through turns.