Adding third will definetly gear it higher giving more top end speed. The positive side would be you will go slightly faster approx. 2-5 mph more on the top end. The negative is that it may lose a bit on the take off, but not so noticable to you though, mainly in a clock. The reasoning in Cen removing it in the Nemesis is that it was designed with the racer in mind. Be that as it is 3rd gear would most likely never get used on any tracks. Too, 3rd gear would also increase the rotating mass in the tranny causing the truck to lose acceleration and precious seconds on the track, this is why most LST race trucks use a forward only conversion which eliminates the reverse and low gears. If bashing is what you plan on doing then it would be a good thing to have as there is no such thing as too much speed, and at about $20 it's worth it. Hope this helps ya. Let us know what you do and how it works out.