The standard ECU can't handle a boost signal from the MAP sensor. The sensor is a frequency rather than voltage type. As the ECU isn't expecting to see a boost signal, it goes into Limited Operating Strategy, fixing the ignition timing and injector pulse length as a "get you home" fix. This will result in a very lean mixture on boost as well as completely the wrong ignition advance, resulting in head, head gasket and piston damage due to severe detonation. Turbo Technics got round this by fitting an electronic frequency limiter to the MAP sensor wiring so that the ECU never saw the boost signal. They also used a digital control unit to fire a 5th injector when on boost (using the coil pulse signal and the voltage from an additional MAP sensor to determine injector pulse width requirement). To manage the ignition timing, they simply shorted both of the ignition timing adjust pins in the octane adjust plug to ground.

I used to run a DOHC with the Turbo Technics kit on it. It made 174 bhp at the flywheel running through a Scorpion stainless exhaust.