Powershifting, no-lift shifting, or flat foot shifting is a method of changing gears in a manual transmission where you do not take your foot off the gas pedal.
Unfortunately, this shifting method is very tough on clutches, so there's a right way and a wrong way of doing it. Cadillac, with the CT4-V Blackwing, has developed a methodology to powershifting that maintains boost pressure of the twin-turbo V6 engine, while reducing the engine load during the shift.
This clever trick involves altering ignition timing, wastegate control, and the bypass valve control. In the end, the desired result is great - a seamless manual transmission shift, all without lifting your foot off the throttle.