If you want to go faster, you need to shift into higher gear. Same thing as with your 1:1 car.
If you take a look into the high speed Gear Set manual, you will see a choice of different final drive ratios. The lower the ratio, the higher your top speed.
With the Tamiya 17.5t brushless motor you can easily choose the lowest ratio shown. I think it is 64:29 ( spur gear : pinion).
64 t spur gear: Tamiya # 51536
29t pinion: Tamiya # 54229
With a bit of luck and fully loaded battery you can reach 25mph (40km/h) with this set up. If this is still not enough there are other ways to optimize the TT-02 's final drive ratio for even more top speed.