[Alan Anderson]

Your drive motors are being commanded only once. Things will work better if you add a While around the drive code, with a Wait of 10 or 20 ms to keep the loop from eating up all the CPU time.

The Gyro Get Angle will have to be duplicated inside the loop for the 90 degree turn. (You can't communicate time-varying values into or out of a loop; they take their inputs once when the loop first begins, and produce an output once the loop finally finishes.)