CARMAKERS tune their cars to suit the average motorist and they also leave a safety margin with their tuning so they can be confident they won't have problems once their cars go into production. Tuners can tune more precisely to achieve a desired outcome, be it more power, torque or fuel economy, and they can play within the manufacturer's safety margin. By some fine-tuning they can extract more power and torque than a manufacturer would dare do. That means you're running closer to the edge when you install a chip, but that doesn't mean you will have a problem. Your best course of action is to choose a chip maker with a long-established, good reputation for doing reliable work, and perhaps with some sort of warranty. Then ask to speak to other owners who have had the same chip fitted to their cars.