Improvements
Battery Supply V2+
I think if I was to build this robot again I would try and use 3 x 1.5 Volt D Batteries for the V2+ supply. These batteries would allow for longer periods between changing due to their larger capacity. I feel this would have allowed for more consistency as the AA batteries would start to lose charge through the maze. This changed the turning characteristics dramatically.
Speed of the robot
Not sure how to increase the speed of the robot without causing it to start crashing into everything but the speed definitely needed to be increased if it was to be competitive in the race. I used the TAMIYA 70168 DOUBLE GEARBOX and selected the 115:1 gear ratio configuration, I found that the 38:1 option was too quick. I think that possibly trialling the TAMIYA 70097 TWIN GEARBOX could have help increase the speed as it has a gear ratio of 58:1 as an option, this would have increased the speed.