I think you need to ask yourself the question; would BMW change the design of their throttle body in order to increase power/torque and reduce fuel consumption by the amounts claimed in that advertising?

There have been a number of different designs of these types of devices sold over the years. I have seen first hand on a couple of old carby cars where they did make marginal differences, particularly to economy, but I think their effect on anything fuel injected is negligible at best.