completly stock, except for slightly shorter tires (1% error). They dont have a true speed limiter the system they use limits speed based on load of the motor, normally stops about 129ish for the 3.27 cars and about 115 with 3.55s. some 99 or 2000s got out without a limiter. The reason they are limited about where they are is the long driveshaft making bad vibrations about 135 with 3.27 and about 120 with the 3.55, and i have not seen any 28" tall tires rated any higher than about 135