Sport Mode on my X5...

[dave the viking]

When you are in S it tells the computer in the car to change to a different set of parameters(stiffen the rear shocks if it is a v8, to increase the throttle response, to hold a gear shift to be longer, to increase the pulls with on the injectors, to give a bit more timing and to increase the voltage to the coils). With the Mx5 it will give it another 50-100 hp.