IMO = In My Opinion
50 Popular Internet Acronyms
I would just keep the spur gear you have and buy a group of pinion gears to find the "sweet spot" you're after. With a 12T motor, your gonna want to start on the conservative side of things. Back in the day the Evader came stock with a 20T motor and a 18T pinion gear with an 88T spur gear. Normally, the "hotter" (more powerful) the motor you use, the tooth count on the pinion gear should go down as well.
What pinion gear do you have now?