help: best pinion and spur for mbx5t

hi guys... my mbx5t is finally alive.. i'm lovin it!! i'm running the mmm 2200 combo
with 4s 5000mah 30c. i using the stock 48t spur with 14t pinion. the truck is running cool and the torque and top end is just about right but i still feel it can take way more. i usually run it in med-large race tracks. in the future.. i'm planning to use a 46t spur with the 14t but right now i only have a spare 15t pinion. what is the best combo?! i'm lookin for more torque. please help! thanks!!