when doing a roll race, applying the brake and throttle at the same time thereby putting more load on the engine and forcing the car into boost.
example:
40 roll - get to 40 mph, step on the brake slightly, when the car slows down apply more throttle to keep you at 40. the turbo will spool since the engine is experiencing more load. 3rd honk slam the gas and get off the brake. the turbo is already spooled so you have instant power instead of a half second delay from spool up
