One of Red Bull’s secrets is a setting on the Renault engine for use on the final crucial lap in qualifying, whereby the ignition is retarded on the over-run, which maintains exhaust gas pressure even when the driver lifts off the throttle. This maintains the performance of the blown diffuser and keeps the downforce up when it’s most needed. It thus avoids the main problem of an exhaust blown diffuser whereby when a driver lifts off the throttle for a corner, the downforce goes missing when you most need it and the rear stability changes.
It’s not something you can do for more than a lap or two as the temperatures go sky high, which damages the engine, but it gives that vital fraction of a second which keeps Red Bull ahead of the rest in qualifying.