An OS .12TZ 3 port is plenty fast in those mini things. Honestly I wouldn't spend $300 on an engine for a car that size especially when you can find other engines for half the price of the R3. Leave that RB motor for nitro sedans like a Mugen, Kyosho, Serpent, GS, etc. You can find the JLR EVO 3 for under $190 easily and it will put out way more power than you need - more than the OS TZ 5 port. Just remember you don't want to spin tires if you plan to race.