The Turbo Launch is a secondary rev limiter built for the MKIV Supra that limits the engine speed to a preset RPM .  It does this by interrupting the ignition signal going to the ECU.  This allows the engine to build turbo boost with the car at rest.  This is great for a car that needs a harder and more consistant launch.  The system is engaged with a switch just before the launch and disengaged just after. 

Dealers for the Turbo Launch system are:
                                                        
MVP Motorsports
                                                        
Suprastore.com
                                                        
Sound Performance
TURBO LAUNCH
Turbo Launch Installation Instructions