I don't thnk there is that much difference between a 13.5 and 17.5, especially if bashing. Modern 17.5s are not slow. You would need to go to a modified motor to start to notice an obvious difference

A bigger factor for you is probably the age of the motor - the original Novaks had a weaker rotor than current motors, and the your gear ratio - there is probably scope to gear up a bit, although the TT-02 is quite limited.

You will probably find a faster brushless motor easier to gear in a TT-02. Bear in mind that a faster motor might start to push the mechanical limits of the car - Tamiya developed it for their sealed brushed motors which are a lot slower.