A couple of things - First, you might have it wrong way 'round, with gearing. There is very little room in the motor bay of the TA06 for excessive gearing changes, and the stock spur is the same one used in their FF03 FWD. It is rather small, and the pinion being of a size that will fit. What size motor are you running, at the moment?

Ideally, you should have a 17.5T if it's brushless (BL) or something like a 27T brushed. Those are smooth, and drift doesn't require tons of RPM, so they are also very easy to modulate, which makes them perfectly suited to drifting. I run the stock spur with a 34T pinion, with a 17.5T BL motor. You would only change gearing, if the present gearing was making the throttle response too quick or too slow.