WOT shifting is a common practice used by drag racers regardless of if they are running turbo, supercharger or naturally aspirated. WOT shifting is accomplished by holding the gas pedal to the floor and never "lifting" off the gas during the shift. The problem with doing so is when you depress the clutch engine RPMs flare up and a brief amount of time is required for the transmission input shaft to slow down. Even the most successful drivers have been known to miss a gear occasionally. It requires complete concentration and lightning quick reactions in order to pull it off.
"Keep the pedal to the metal, blip the clutch, and grab the next gear. Do it fast enough before the redline, and your reward will be a zero lag, constant boost shift."
When you WOT shift, your engine is still producing peak power through the shift. With the clutch released, the engine revs up. This increase in RPMs and the full output power of the engine makes it very difficult for the synchros in your transmission to engage. The result means that WOT shifting can be very difficult and potentially damaging to your transmission.