I would like a little extra power from the 2010 BMW X1 23d I have just bought and have read about a power chip made by Chip Express in England that is apparently a self-install chip connected 'down south' of the ECU in the car, so they claim your warranty is not void. Have you had any experience with how easy these chips are to install and whether they actually achieve what they claim?
We haven't had any experience with the chip you refer to, but have had some with other chips that have been offered here in the past. Yes they can work, but they do so by taking the engine calibration closer to the edge than the carmaker would dare do with safety. In my view they would clearly affect the warranty.