To tune a car means to improve the stock equitment, to benefit preformance or looks. For example people tune a car by changing the exhaust system, changing the rims, or adding a turbo-chrager. Tuned cars can be noticeable if it is more cosmetic changes, but others are not noticable until the preformance is tested. Preformance tuner cars can be tuned several ways. Some are tuned for speed around a track, but others are set up to be better in off-road conditions.