Uk spec 250 CLA 4matic has a sport button which does nothing more than hang on to a lower ratio for longer, which used to leave me begging for the thing to change up a gear. I have found the answer, turn the ESP off. The car now changes gear when it should, the engine releases more torque and doesn't fall over itself every time you show the car a corner. I don't condone irresponsible driving but this actually makes the handling more predictable, the 4matic 4 wheel drive looking after the rest. Apologies if this has been raised before as I have just joined the forum today.