there're both 3 and 5 ports tz12, what's the color of yr heatsink?
silver heatsink will be 5 ports; blue will be 3.

OS engines are one of the most easy to tune. tz12 has good punch low-mid; highend will be abit lacking. if yr track is small to medium; tz12 shld be have enough power....try to gear slightly higher to take advantage of the lowend punch and gain better topspeed.